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UNIVERSITY  OF  CALIFORNIA 
AT   LOS  ANGELES 


How  TO  MAKE  INVENTIONS; 


OR, 


INVENTING  AS  A  S6IENSE  AND  AN  ART. 


A     PRACTICAL     GUIDE    FOR    INVENTORS. 


EDWARD  P.  VHOMPSON,  M.E., 

Member  American  Society  of  Me  -hanical  Engineers  ;  Member,  an  Examiner 

and  an  ex-Manager  Amer     .n  Institute  of  Electrical  Engineers  ; 

Member  New  York  Electrical  Society. 


FIRST    EDITION. 


NEW  YORK  : 

D.  VAN  NOSTRAND  CO., 
23  MURRAY  AND  27  WARREN  STREETS. 


TO 

MY  ALMA  MATER, 
THE 

STEVENS  INSTITUTE  OF  TECHNOLOGY, 

THIS 
BOOK   IS   DEDICATED. 


Copyright,  1891,  by  EDWARD  P.  THOMPSON. 


THE  style  adopted  is  that  of  a  lecture,  and,  therefore,  it  is  hoped  that  the 
use  of  personal  pronouns  may  be  overlooked. 

The  object  in  view  is  to  make  a  mere  beginning  in  the  establishment 
of  Inventing  as  a  Science  and  an  Art,  but  especially  to  present  conclu- 
sions arrived  at  in  the  study  of  inventors  and  inventions  in  order  that  the 
capacity  of  inventors  may  be  enlarged.  If  even  a  single  useful  invention 
results  from  the  perusal  of  this  book,  I  shall  feel  that  the  time  has  not  been 
spent  in  vain. 

Not  knowing  how  a  book  with  such  a  title  would  be  accepted,  preliminary 
notices  were  distributed  soliciting  subscriptions  contingent  upon  publication. 
I  am  greatly  indebted  to  those  who  so  kindly  sent  in  such  subscriptions,  and 
especially  to  those  subscribers  who  wished  me  success.  The  Electrical  World 
(New  York)  I  also  thank  for  inserting  a  series  of  paid  articles  on  this  subject, 
prepared  and  contributed  by  me  during  the  year  1884. 

Much  encouragement  for  continuing  the  development  of  the  subject-matter 
was  given  by  Mr.  T.  Commerford  Martin,  editor  of  The  Electrical  Engineer 
(New  York),  and  Mr.  George  H.  Guy,  editor  of  Electricity  (Chicago),  who  so 
kindly  invited  me  to  deliver  a  lecture  upon  this  subject  before  the  New  York 
Electrical  Society  in  1890. 

As  may  be  expected,  the  inventor  will  in  no  way  be  relieved  of  tedious 
labor  by  following  any  instructions  contained  in  this  book.  I  am  inclined  to 
believe  that  this  will  not  be  the  basis  of  any  criticism  which  may  be  rendered 
by  any  opponents  or  prejudiced  minds  ;  because  I  have  learned  and  am  more 
and  more  impressed  with  what  I  believe  to  be  a  fact  that  a  lazy  inventor  has 
never  yet  been  born.  No  day  laborer  makes  as  many  hours  a  day.  The 
physician,  missionary,  and  other  philanthropists  cannot  show  a  better  record 
for  diligence  of  both  the  body  and  the  mind.  In  writing  this  book  I  have 
borne  this  in  mind,  and  have  felt  that  there  was  no  danger  of  making  those 
suggestions  and  giving  that  instruction  which  would  be  rejected  by  the  inventor 
simply  because  much  work  was  involved.  I  have  recognized,  however,  that 
humanity  does  not  like  things  too  dry  and  abstract,  and,  therefore,  I  have 
aimed  in  making  the  matter  as  easily  understood  as  possible  by  means  of  illus- 
trations and  as  few  as  possible  of  intricate  and  unusual  technical  words  and 

210993: 


31 


phrases.  It  certainly  is  necessary  for  an  inventor  to  have  knowledge,  but  not 
to  be  a  great  literary  scholar. 

The  work  is  particularly  exceeding,  when  it  is  remembered  that  an 
inventor,  according  to  Benjamin  Franklin,  must,  in  making  a  great  invention 
pass  through  the  three  following  stages,  namely  :  i.  He  starts  to  do  that  which 
others  say  is  impossible.  2.  When  he  claims  to  have  succeeded,  people  believe 
him  not.  3.  When  his  invention  comes  into  commercial  use,  hosts  of  inventors 
appear  who  claim  to  have  done  the  same  thing  before. 

One  of  the  most  important  elements  for  ensuring  success  in  any  under- 
taking is  preparation.  At  the  present  time,  the  World's  Fair  at  Chicago  is  a 
"future  event,"  but  its  success  depends  more  upon  what  is  done  before,  than 
after  the  day  of  opening.  Committees  are  appointed  for  making  preliminary 
arrangements.  A  site  must  be  chosen  first,  as  to  location  in  the  country  and 
then  as  to  the  particular  portion  of  the  chosen  city.  An  engineer  is  appointed 
for  each  department  of  industry.  A  business  department  with  its  managers 
and  clerks  must  be  established.  The  people  must  be  informed  and  educated 
up  to  the  idea  of  the  benefits  and  attractions,  or  the  attendance  will  be  small. 
All  this  is  preparation.  The  drift  of  this  book  is  similar.  It  is  intended  as  a 
means  of  preparation  rather  than  as  a  collection  of  mathematical  rules  to  be 
followed  in  order  to  make  an  invention.  Napoleon  is  noted  for  the  display  of 
genius  in  many  of  his  manoeuvres,  whereby  he  conquered  nations  under 
circumstances  which  depended  upon  instantaneously  conjured  plans  developed 
mentally  and  carried  out  physically  ;  but  it  must  be  remembered  that  if  he  had 
not  spent  preliminary  hours  in  thought,  made  scores  of  maps  of  the  proposed 
attacks,  instructed  his  inferiors  as  to  all  the  probable  and  improbable  haps  and 
mishaps,  studied  the  lives  of  other  successful  and  unsuccessful  soldiers,  and  the 
histories  of  other  nations,  his  genius  would  have  counted  for  so  little  that  there 
would  probably  have  been  no  exhibition  of  the  same. 

NEW  YORK.  E.  P.  T. 


CHAPTER     I. 
INVENTION,  THE  GREATEST  SCIENCE  IN  THE  WORLD. 


TATHAM  has  said  : — "  Invention  is  the  happiness  of  man." 
Edison  has  said  that  he  is  happiest  while  inventing.  The  Book 
of  Truth  says  :  "  It  is  more  blessed  to  give  than  to  receive." 
Inventors  may  say  : — "  We  give  to  the  world  more  than  we  receive. 
We  are  happy  in  inventing.  We  have  often  become  poor  while 
the  world  has  become  rich  by  our  inventions.  Even  when  we 
have  made  our  thousands,  the  world  has  netted  its  millions." 

Of  all  the  physical  and  mental  sciences,  which  is  the  great- 
est in  the  world  ?  Is  it  Chemistry,  Natural  Philosophy,  Physi- 
ology, Mineralogy,  Geology,  Electricity,  Mental  Philosophy  or 
Metaphysics  ?  Most  emphatically,  No  !  The  sun  furnishes 
light,  but  of  what  value  is  the  light  if  we  use  it  not?  The  sci- 
ences just  named  furnish  knowledge.  Of  what  value  is 
knowledge  if  it  is  not  used  ?  Invention  is  the  greatest  science, 
if  measured  by  its  usefulness  to  mankind,  because  it  gives  to  the 
world  the  practical  benefit  of  the  other  sciences.  It  is  the  sci- 
ence which  applies  knowledge  to  useful  purposes.  Without 
invention,  Chemistry  and  Physics  are  practically  worthless. 
Physics  says: — "  Heat  expands."  Invention  applies  this  principle 
and  builds  a  steam  engine  whose  power  is  due  to  the  expansion 
of  water  by  heat.  Chemistry  and  Mineralogy  result  in  the  dis- 
covery of  phosphorus  and  sulphur.  Invention  makes  the  match, 
one  of  the  most  useful  and  wonderful  and  almost  magic-like 
inventions  ever  made.  Physics  teaches  that  speaking  vibrates 
the  air  and  diaphragms,  and  that  an  electric  current  can  be 
rapidly  varied  from  zero  to  maximum  and  from  maximum  to 
zero.  Invention  applies  these  principles  to  the  electrical  trans- 
mission of  speech.  Geology  exhibits  the  structure  of  the  earth, 
Invention  produces  thousands  of  Green's  driven  wells. 


CHAPTER     II. 
THE  FOUNDATION  OF  THE  SCIENCE  OF  INVENTION. 

EVER  since  the  time  of  Bacon,  any  given  science  has  been 
developed  by  classifying  facts  and  establishing  principles  thereon. 
Before  the  time  of  Bacon,  little  progress  was  made  in  any  sci- 
ence because  principles  were  proclaimed  and  then  facts  sought 
to  uphold  the  principles.  The  new  process  of  Bacon  is  called 
the  inductive  system  of  developing  a  science  ;  and  the  earlier 
process,  the  deductive  system. 

The  development  of  a  science  by  searching  for  and  record- 
ing facts  and  establishing  principles,  does  in  itself  assist  the 
science  to  grow  ;  thus,  the  science  of  Physiology,  having  been 
recorded  in  publications  under  classified  principles,  enables  each 
future  generation  of  physicians  to  acquire  easily  the  principles, 
and  to  add,  from  time  to  time,  valuable  facts  which  either 
strengthen  old  principles  or  show  their  fallacy.  The  science  of 
Chemistry  forms  the  knowledge  of  the  chemist,  who,  knowing  it 
in  its  present  condition,  can  make  use  of  the  experience  of 
others,  and  add  to  its  records,  because  he  knows  the  record  of 
the  past.  So,  also,  with  the  more  abstract  sciences,  as  those  of 
Political  Economy,  the  Sciences  of  Civilization,  Religion  and 
Psychology.  Before  the  time  of  Bacon,  any  one  who  desired  to 
add  to  the  knowledge  of  the  world  worked  in  the  dark.  He 
knew  little  because  the  knowledge  before  him  was  not  intel- 
ligently and  conveniently  collected  and  classified  for  his  use. 

Philosophical  speculations  occupied  more  time,  and  were 
considered  more  valuable  than  experiment.  The  Royal  Society 
in  olden  times  spent  several  meetings  in  discussing  whether  a 
pail  of  water,  with  a  dead  fish  in  it,  weighed  more  or  less 
than  a  pail  of  water  containing  a  live  fish.  Finally,  a  member 
who  was  certainly  ahead  of  his  age,  boldly  and  unexpectedly 
settled  the  question  by  actually  weighing  the  pail  of  water  under 
the  two  conditions. 

An  inventor,  who  expects  the  greatest  success  in  conceiving 
and  developing  an  invention,  should  be  acquainted  with  princi- 
ples of  inventing,  based  upon  facts  evolved  by  the  study  of 
former  inventions  ;  or  else  he  works  in  the  dark  ;  trusts  to  get- 
ting his  ideas  by  accident  ;  or  leaves  his  inventions  in  such  a 
crude  state  as  to  render  them  practically  worthless.  The  sci- 
ence of  Civilization  deals  with  the  greatest  events  of  history  ; 
drawing  therefrom  the  principles  upon  which  the  science  is  based. 
This  book  attempts  similarly  to  establish  the  science  of  Inven- 
tion upon  the  history  of  the  greatest  inventions  and  inventors. 


3 
CHAPTER    III. 

THE  PRIMARY  POWER  FOR  DRIVING  AN  INVENTOR. 


IN  becoming  a  business  man,  a  professor,  an  electrical  engi- 
neer, or  engaged  in  any  occupation,  the  first  requisite  is  to 
have  a  love  for  it.  If  a  youth  is  to  be  a  lawyer,  he  should  first 
determine  if  he  believes  he  would  enjoy  that  profession.  If  he 
is  to  prepare  for  college,  he  must  first  determine  if  he  prefers  a 
profession  to  a  business  career.  Having  decided  what  he  likes, 
let  him  proceed  with  a  concentration  of  all  his  energies,  and  he 
is  sure,  nine  times  out  of  ten,  to  succeed.  The  very  enjoyment 
of  his  work,  and  belief  in  his  own  power  to  succeed,  will  do 
more  for  him  than  any  other  one  element,  because  all  other  ele- 
ments are  comparatively  useless  without  well-directed  and 
honest  ambition. 

Love  of  inventing  may  be  natural  or  acquired.  It  grows 
with  practice.  The  more  one  invents,  the  more  he  loves  to  con- 
tinue. The  natural  love  of  cyling  or  playing  games  grows  until 
it  may  be  said  to  be  acquired.  The  more  one  invents,  the  more 
he  loves  that  employment. 


CHAPTER     IV. 
How  TO  LEARN  WHAT  TO  INVENT. 


BEFORE  the  introduction  of  the  telegraph  system,  the  quickest 
communication  of  ideas  between  two  points  of  considerable 
distance  was  by  post,  express  or  special  messenger.  Great  in- 
convenience was  the  consequence  and  often  ensued  the  loss  of 
money  and  non-fulfillment  of  duties  and  obligations,  in  cases  of 
death  and  important  business  transactions.  Everything  was 
done  by  the  government  and  private  corporations  to  provide 
means  for  lessening  the  time  for  transmitting  messages.  The 
public  realized  the  importance  of  saving  time.  Probably  thou- 
sands of  people  realized  the  inconvenience  and  injury  done  by 
slowness  of  transmission.  Every  one,  substantially,  may  be  said 
to  have  recognized  the  inconvenience,  the  trouble  and  the  dif- 
ficulty. They  knew  that  it  would  take  days  and  even  months 
for  their  letters  to  reach  certain  parts  of  the  world. 
They  knew  that  in  the  case  of  death  of  one  of  the 


family  the  funeral  would  occur  before  those  at  a  cer- 
tain distance  could  receive  the  news.  They  knew  that  when 
a  great  event,  such  as  a  battle,  was  expected  to  take  place  in  a 
foreign  country,  ten  days  or  more  would  elapse  before  they 
could  learn  the  result.  They  knew  that  during  a  journey  of  a 
colleague  on  important  business  through  the  country  they  could 
know  his  whereabouts  and  successes  and  failures  with  from  one 
day  to  several  weeks'  delay.  In  short,  they  were  strongly  con- 
vinced of  the  existing  difficulty.  They  had  no  doubt  as  to  the 
usefulness  of  any  means  which  would  remove  the  difficulty. 
Some  were  resigned  as  if  to  a  fate.  Others  hoped  and  even  pre- 
dicted wonderful  improvements.  But  who  was  it  that  not  only 
realized  the  difficulty,  but  had  faith  that  the  trouble  could  be 
removed  ?  Who  was  it  that  not  only  talked  with  friends  on  his 
homeward  ocean  trip  about  the  inconvenience  of  slow  transmis- 
sion of  messages,  and  not  only  believed  in  a  remedy,  but  ex- 
pressed in  words  that  he  believed  the  difficulty  could  be  re- 
moved ?  He  talked  with  others  more  educated  than  himself  in 
order  to  glean  knowledge  and  make  use  of  it  for  the  public. 
This  is  a  fact,  therefore,  based  upon  history,  that  Morse,  the  in- 
ventor of  the  telegraph,  recognized  the  existence  of  a  certain 
need  in  the  world,  and  not  only  that,  but  also  believed  there 
was  room  for  improvement ;  and  on  top  of  this  knowledge  and 
belief  he  had  faith,  and  followed  up  his  faith  by  diligence  and 
actual  work.  This  fact  is  apparent  also  in  the  study  of  other 
inventions.  It  is  the  public  that  realizes  the  existing  difficul- 
ties, while  it  is  the  inventor  who  follows  up  his  belief  by  his 
diligence.  Take  the  case  of  the  invention  of  the  telephone. 
The  public  appreciated  the  value  of  the  telegraph  for  communi- 
cating from  one  part  of  a  country  to  another,  but  to  telegraph 
from  one  part  of  a  city  to  another  amounted  to  little  more  than 
sending  a  special  messenger.  It  was  the  inventor  who  not  only 
recognized  the  difficulty,  but  also  undertook  a  personal  task  of 
removing  it. 

The  public  realized  the  danger  of  boiler  explosions.  In- 
ventors did  also,  but  they  went  further  and  undertook  to  prove 
that  they  could  remove  the  difficulty,  and  as  a  result  invented 
the  safety  valve  and  improvements  of  construction  and  opera- 
tion, whereby  most  boiler  explosions  of  the  present  date — which 
are  exceedingly  scarce  in  proportion  to  the  number  of  boilers — 
arise  from  sheer  carelessness.  Public  opinion  at  one  time,  and 
only  lately,  denounced  electric  arc  lighting,  because  it  was  dan- 
gerous. The  cry  against  high  tension  currents  aroused  inventors 
to  a  belief  in  means  for  eliminating  the  danger,  and  they  have 
already  and  almost  perfectly  succeeded,  whereby  the  accidents 


are  fewer  in  actual  number,  although  the  circuits  have  increased 
hundreds  of  miles.  Among  smaller,  but  very  important  inven- 
tions, may  be  mentioned  the  crank-and-gearing  combination 
with  shutters  or  blinds.  People  were  aware  of  the  danger  of 
catching  a  cold,  letting  in  flies  and  mosquitoes,  and  of  other 
difficulties  connected  with  shutting  the  blinds.  The  inventor 
also  realized  the  difficulties,  but  in  addition  believed  that  he 
was  the  one  to  remedy  it,  the  result  being  means  for  operating 
shutters  by  merely  turning  a  small  crank  inside  of  the  house.  A 
study  of  the  invention  of  the  spring  roller  for  window  shades, 
from  which  fortunes  have  been  made,  exhibits  the  same  fact. 
The  principle  derived  may  be  stated  thus  : 

Any  given  individual  takes  a  step  toward  becoming,  or  im- 
proving himself  as  an  inventor,  who  studies  the  need  of  the 
public  ;  learns  the  difficulties  connected  with  that  department  of 
art  or  industry  in  which  the  need  exists  ;  excites  his  mind  with 
the  belief  that  he  can  provide  means  to  remove  the  difficulties  ; 
and  proceeds  with  diligence  toward  the  solution  of  the  problem. 

The  truth  of  this  principle  is  strengthened  by  its  negative 
aspects.  Suppose  the  first  step  should  be  not  to  study  the  need 
of  the  public.  The  consequence  would  follow  in  many  cases, 
in  the  production  of  useless  inventions — i.  e.,  those  which  ac- 
complish results  not  wanted.  This  often  does  occur.  As  an 
illustration,  parlor  skates  may  be  mentioned.  An  inventor  of 
an  improved  roller  skate  for  to-day  is  an  inventor  of  that  which 
has  no  market,  as  skating  rinks  have  gone  out  of  fashion  and 
lost  their  popularity.  It  is  something  which  the  public  does  not 
want  at  present,  even  though  it  did  formerly  pay  a  tribute  of 
many  thousand  dollars  to  the  early  inventors  and  improvers  of 
the  parlor  skate. 

The  second  element  of  the  principle  before  stated  consists 
in  learning  the  difficulties  connected  with  that  department  of 
art  or  industry  in  which  the  need  exists. 

If  there  is  any  one  difficulty  in  connection  with  any  depart- 
ment of  art,  the  would-be  inventor  may  be  sure  of  reward  if  he 
succeeds  in  overcoming  the  difficulty.  How  is  he  to  become 
aware  of  the  difficulty  ?  He  is  to  make  a  business  or  study  to 
this  end.  If  he  is  engaged  with  a  manufacturer  he  can  daily 
become  acquainted  with  difficulties  which  prevent  the  manu- 
facturer from  clearing  as  much  profit  as  he  should.  At  one  time 
so  much  trouble  was  experienced  at  sea  by  the  untimely  jump- 
ing of  the  safety  valve  that  steam  navigation  was  well  nigh 
abandoned.  The  engineer  of  the  boiler  manufacturer  viewed 
the  difficulty  as  something  to  be  overcome,  and  solved  the  same 
by  substituting  a  spring  for  the  weight  which  controlled  the 


valve  If  he  is  a  student  or  scholar  of  science,  he  can  become 
acquainted  with  difficulties  by  studying  any  particular  art.  If 
he  is  a  business  man  he  can  learn  difficulties  by  the  habit  of 
observation  of  difficulties  met  with  by  himself,  In  connection 
with  his  own  business,  any  man  can  learn  some  difficulty  it  he 
will  only  keep  his  wits  about  him  and  be  on  the  lookout.  He 
may  meet  it  in  traveling,  in  business,  in  his  home,  in  his  con- 
versation with  others,  in  the  newspapers  and  in  other  directions. 
At  the  present  moment  exist  problems  well  known  to  many,  but 
yet  unsolved,  and  of  all  degrees  of  magnitude,  and  in  all  depart- 
ments of  every  art.  Since  the  learning  of  difficulties  is  one  of 
the  elements  of  the  first  principle  underlying  the  science  of  in- 
vention, it  seems  but  proper  that  some  should  be  given  at  least 
for  the  sake  of  illustrating  what  is  meant  by  a  "  difficulty  "  for 
an  inventor  to  solve.  This  matter  is  treated  in  the  chapter  on 
"Problems  in  Invention." 


CHAPTER    V. 
HINDRANCES  TO  THE  PROGRESS  OF  INVENTION. 

SOME  are  desirous  of  being  inventors.  They  know  they  have 
a  love  for  it.  They  admit  that  there  is  room  for  improvement 
and  for  original  invention.  They  have  studied  the  principles  of 
science  or  of  a  particular  art.  They  believe  that  others  may 
and  will  invent.  Ask  them  why  they  do  not  invent.  The  invari- 
able reply  is  that  they  believe  they  possess  no  genius  or  inven- 
tive faculty.  They  imply  that  some  have  been  born  and  gifted 
with  what  they  have  not.  This  is  not  true.  Every  man  has 
more  or  less  power  of  inventing.  Every  day  every  one  busily 
occupied  uses  his  power  or  faculty  of  inventing  when  he  plans, 
in  imagination,  his  business  of  the  day,  or  whenever  he  thinks 
of  the  best  way  of  carrying  out  an  idea.  Let  one  once  believe 
that  he  does  possess  the  power  to  invent  and  it  will  not  be  long 
before  he  will  know  that  the  field  of  invention  is  shut  against 
none.  From  observation  I  conclude  that  the  following  princi- 
ple is  true  :  A  belief  of  an  individual  that  he  himself  does  not 
possess  genius  or  the  power  to  invent  is,  in  itself,  a  hindrance  to 
the  action  of  that  power. 

The  corollary  which  follows  is  :  An  individual  who  will 
admit  that  he  possesses  a  power  of  inventing,  to  a  greater  or 
less  extent,  may  become  an  inventor  by  the  proper  use  of  his 


knowledge.  Suppose  that  the  inventor  of  the  device  for  thread- 
ing needles  insisted  previously  upon  the  assumption  that  he  had 
no  genius.  He  did  not  so  assume.  Consequently  he  received 
an  annual  income  of  $10,000  from  the  sales  of  his  patented 
needle-threader,  which  was  at  one  time  so  popular  a  device. 
The  inventor  of  the  roller  skate  cleared  nearly  $1,000,000,  al- 
though during  only  the  last  few  years  of  the  term  of  the  patent. 
Will  any  civilized  white  man  assume  he  has  no  inventive 
faculty  or  genius  when  it  is  a  fact  that  the  Patent  Office  re- 
cords show  that  colored  men  are  inventors  ?  I  am  personally 
acquainted  with  a  colored  man  who  has  not  only  made  electrical 
inventions  and  received  letters  patent  of  the  United  States, 
but  has  sold  the  same.  His  extreme  confidence  in  his  ability  to 
invent  is  easily  apparent  to  those  who  know  him.  Some  of  his 
inventions  show  a  high  type  of  invention  ;  therefore  it  seems  but 

Proper  that  due  honor  should  be  given  by  mentioning  his  name, 
refer  to  Granville  T.  Woods,  formerly  of  Cincinati,  Ohio. 


CHAPTER  VI. 

SUGGESTIVE  IDEAS. 


WHILE  I  admit  the  plausibility  of  an  inventor's  working  ex- 
clusively upon  one  subject,  yet  it  is  often  true  that  he  remains 
too  long  in  one  line  of  thought  or  channel.  A  certain  inventor 
(Gatling)  failed  in  protecting  a  successful  screw  propeller,  after 
working  upon  that  subject  for  a  long  time  ;  but  as  soon  as  his 
attention  was  drawn  to  another  line  of  work  (guns)  his  enthu- 
siasm revived  and  he  soon  made  a  commercial  success.  Frank  J. 
Sprague  stated  at  a  meeting  of  the  American  Institute  of  Elec- 
trical Engineers,  that  upon  his  hearing  of  the  great  success  of 
Brush,  Thomson,  Edison,  and  others  in  electrical  inventing,  he 
concluded  there  was  room  for  him  also,  and  therefore  made  valu- 
able inventions,  left  the  Army,  and,  as  is  well  known,  in  a  won- 
derfully short  time  succeeded  both  scientifically  and  financially. 
If  success  does  not  follow  after  a  reasonable  time  in  any  given 
direction,  try  other  departments. 

It  has  often  been  stated  that  the  way  to  invent  is  to  think, 
and  keep  on  thinking.  It  is  almost  impossible  for  one  to  think 
unless  he  has  whereof  to  think.  He  must  receive  certain  im- 
pressions from  without  before  he  has  anything  upon  which  to 
concentrate  his  mind.  In  short,  as  in  all  cases  where  good  is  to 


be  obtained,  inventing  involves  systematic  and  diligent  mental 
and  bodily  work.  The  inventor  must  be  given  a  suggestive  idea. 
Probably  an  invention  was  never  made  except  by  receiving 
some  kind  of  impression  from  outside  of  the  mind.  By  study- 
ing past  inventions  and  inventors  it  is  found  that  certain  sug- 
gestive ideas  have  prompted  inventors  over  and  over  again,  and 
continue  to  give  to  the  world  greater  and  greater  reward. 

The  following-headed  paragraphs  contain  some  of  those 
suggestions  which  have  heretofore  prompted  inventors: 

A  device  to  do  automatically  that  which  has  been  done  by  hand. — 
An  early  example  is  that  of  the  eccentric.  A  boy  was  obliged 
to  turn  a  valve  to  let  in  the  steam  at  each  stroke  of  the  piston. 
A  later  example  is  an  automatic  device  which,  exactly  at  the 
end  of  five  minutes,  in  a  long  distance  telephone  system,  cuts  off 
the  subscriber's  line  from  use.  The  operators  are  apt  to  give 
subscribers  too  long.  Such  inventions  are  among  the  most  valu- 
able known.  They  save  cost  of  manual  labor,  prevent  injury 
and  accident  due  to  neglect  of  man,  and  often  do  the  work 
much  better.  Progress  of  invention  in  this  direction  can  be 
made  by  taking  note  of  what  is  at  present  done  by  hand,  and 
considering  if  it  would  not  be  advantageous  to  have  a  device 
which  will  accomplish  the  same  thing  automatically.  The  work- 
ing out  of  a  device  to  do  it  usually  requires  only  ordinary  intel- 
ligence. As  soon  as  the  boy  wanted  to  go  out  to  play  ball  and 
not  let  the  steam  engine  stop,  it  occupied  but  a  short  time  to 
^rig  up  a  string  and  lever  between  the  valve  and  one  of  the  mov- 
ing parts  of  the  engine  and  make  the  engine  take  care  of  itself. 
To  make  this  class  of  invention,  therefore,  closely  observe  what 
is  at  present  done  by  hand  in  the  different  departments  of  manu- 
facture, electrical  installations,  commercial  traffic,  at  home,  on 
the  street,  railroad,  and  everywhere.  Again,  if  three  motions  of 
the  hand  are  necessary  to  operate  an  apparatus,  try  to  make  the 
device  attend  to  some  of  those  motions. 

Preventing  Loss  of  Life  and  Property. — When  a  serious  catas- 
trophe occurs  on  a  railway  system,  in  the  street,  or  anywhere,  it 
is  the  duty,  or  at  least  the  function,  of  an  inventor  to  study  into 
the  cause  of  the  accident  and  discover,  either  by  personal  in- 
spection, by  official  reports,  or  by  the  most  reliable  means  at 
hand,  the  exact  details  of  operation  of  the  system  before,  dur- 
ing, and  after  the  accident.  An  invention  which  will  in  prin- 
ciple prevent  the  same  kind  of  accident  in  the  future  is  that 
which  is  likely  to  become  useful  when  fully  developed  and  ap- 
plied. This  has  been  the  manner  in  which  valuable  safety  de- 
vices and  systems  have  in  the  past  been  invented  and  introduced, 
and  therefore  it  will  be  a  safe  rule  to  follow  in  the  future. 


Since  the  invention  and  introduction  of  the  automatic  brake 
system  of  George  Westinghouse,  Jr.,  and  his  associate  inventors, 
loss  of  life  and  property  has  been  enormously  reduced. 
He  and  they  provided  means  for  stopping  a  train  moving 
at  a  high  speed  within  a  distance  several  times  less  than 
could  be  done  by  hand,  and  therefore  in  the  case  of  emergency 
the  train  could  be  stopped  before  an  accident  was  possible.  In 
many  other  ways,  accidents  have  been  prevented  by  this  inven- 
tion, which  possesses  utility  in  a  very  high  degree.  But  there  is 
a  class  of  accidents  impossible  to  prevent  by  the  automatic 
brake  system.  Observation  of  records  in  the  newspaper  shows 
that  two  railway  accidents  per  week  occur  on  an  average  in  the 
United  States,  with  loss  of  life  and  property  or  both.  It  has  been 
proposed  through  the  press  that  these  accidents  be  made  a  sub- 
ject of  legislation  by  appointing  a  committee  to  study  into  the 
cause  of  the  accidents  ;  to  learn  if  there  are  or  maybe  means  in 
existence  for  preventing  them;  to  determine  if  the  railway  com- 
panies shall  be  forced  to  adopt  any  invention  or  inventions 
adapted  to  prevent  certain  kinds  of  accidents  ;  and  to  consider, 
in  general,  the  best  welfare  of  the  public  in  this  connection.  In 
a  similar  manner,  other  departments  of  art  could  be  considered 
in  regard  to  means  for  preventing  loss  of  life  and  property  by 
navigation,  chemical  manufacture,  and  electric  lighting  and 
power.  Some  inventions  in  safety  devices  for  railway  systems 
are  ludicrously  interesting,  but  at  the  same  time  plausible.  For 
example,  there  was  an  exhibition  in  this  city  of  a  system  whereby, 
upon  two  trains  approaching  each  other,  the  whistles  on  both 
locomotives  are  automatically  operated  so  as  to  notify  the  en- 
gineers of  danger.  The  whistle  of  either  train  is  operated 
through  electric  circuits  by  the  other  train,  and  vice  versa,  when 
the  trains  approach  within  a  predetermined  distance  of  each 
other.  It  is  appropriately  called  "  The  Tooting  System." 

How   many   hundreds  of   steam   boilers  would  explode   if 
•  equipped  with  only  steam  gauge  and  water  signal,  and  not  with 
a  safety  valve,  which  operates  in  case  of  danger,  whether  the  en- 
gineer is  asleep,  intoxicated,  careless,  or  entirely  absent. 

Reducing  Cost  of  Manufacture,  or  of  the  Cost  of  the  Products 
of  Manufacture. — The  now  well-known  wire  hat-and-clothes 
hook  costs  only  a  small  fraction  of  the  former  cast  iron  hook  and 
is  easier  to  place.  The  late  embroidering  machine  does  the 
work  of  dozens  of  factory  girls  at  less  cost  and  produces  supe- 
rior work.  The  first  conception  of  a  telegraph  system  before 
Morse's  new  alphabet  system  was  by  having  a  circuit  closer  on  the 
main  line  for  each  letter  and  figure.  The  cost  of  a  line  of  36 
wires  from  New  York  would  be  so  great  as  to  discourage  capital 


10 

It  never  even  came  into  use.  The  first  incandescent  lamps  were 
half  as  intricate  as  an  arc  lamp.  The  present  machine  for  setting 
up  type  by  striking  keys  like  a  typewriter,  although  practical,  is 
no  doubt  as  intricate  in  comparison  to  probable  later  improve- 
ments, as  the  first  sewing  machines  were  in  relation  to  the 
present  forms,  which  themselves  are  continually  undergoing  re- 
duction in  cost  of  manufacture.  Aim,  therefore,  to  so  modify 
any  given  device  that  the  same  may  be  manufactured  in  larger 
quantities  for  the  same  money,  or  so  that  the  products  of  that 
machine  may  be  produced  more  rapidly.  This  is  accomplished 
most  probably  by  a  radically  different  construction,  whereby 
the  cost  of  the  castings  for  instance  may  be  less  ;  or  whereby 
the  number  of  moving  parts,  levers,  wheels,  &c.,  may  be  less- 
ened ;  or  whereby  the  result  is  obtained  by  the  application  or 
combination  of  different  mechanical  principles.  Aluminium 
was  first  obtained  chemically,  and  sold  at  from  $3  to  $6  per  Ib. 
The  principle  of  making  its  oxide  a  conductor,  by  mixing  car- 
bon with  it,  and  heating  by  an  electric  current,  was  applied,  so 
that  now  it  costs  but  $i  per  Ib.  Every  now  and  then  we  learn 
of  these  wonderful  inventions  for  getting  some  old  results  at  a 
much  less  cost.  It  is  one  of  the  most  profitable  and  accessible 
fields  for  those  who  are  willing  to  face  the  problems  boldly. 

By  "less  cost"  or  "cheaper"  is  evidently  not  meant 
"  poorer  material  "  or  "careless  work." 

Fair  Competition. — The  fact  that  one  inventor  holds  a  monop- 
oly is  not  necessarily  a  reason  why  a  second  inventor  cannot 
share  the  profits.  There  is  generally  a  chance  of  inventing  that 
which  will  accomplish  the  same  result  without  infringing  the 
patent.  Occasionally  this  is  impossible,  but  oftener  it  is  possi- 
ble. It  is  better  for  the  community  that  there  should  be  two 
competing  parties.  It  is  probable  that  both  parties  will  reap 
fortunes.  The  author  does  not  encourage  infringement,  but  fair 
competition  among  inventors,  and  therefore  greater  progress  in 
the  arts.  The  inventor  who  succeeds  in  "  getting  around  "  a 
certain  patent,  and  avoids  any  doubt  of  infringement,  does  only 
right  to  the  community—/,  e.,  to  the  majority — andbreaks  no  laws. 
An  example  is  that  illustrated  by  the  great  monopoly  once  held 
by  the  telegraph  company.  Prof.  Bell  accomplishes  even  a  bet- 
ter means  of  rapid  transit  of  messages  for  moderate  distances, 
as  measured  by  the  profits  to  the  company  ;  while  the  telegraph 
company  to  all  appearances  is  not  at  all  poor  ;  neither  are  their 
numerous  detail  patents  infringed,  nor  would  the  original,  but 
expired,  patents  have  been  infringed  had  the  telephone  been 
invented  at  the  beginning  of  telegraphy.  The  same  general  re- 
sult was  accomplished  by  non-infringing  means.  There  a-re 


11 

many  illustrations  of  this  principle  ;  so  that  inventors  need  not 
stop  from  courtesy  to  other  inventors,  from  fear  of  injuring  their 
business.  The  community  demands  fair  competition  among  in- 
ventors as  well  as  among  manufactures  and  dealers.  Proceed, 
therefore,  without  fear  to  find  out  just  how  broadly  a  certain 
patented  monoply  is  covered,  and  exert  the  utmost  power  to 
accomplish  the  same  or  better  results  by  non-infringing  means. 

Slight  Circumstances  Lead  to  Invention, — For  example,  Prof. 
Short,  of  the  Short  Electric  Railway  Co.,  visited  the  Electrical 
Exhibition  held  several  years  ago  at  Chicago,  and  while  there, 
became  so  interested  in  electric  railways  by  observing  a  model 
of  one,  that  from  that  moment  he  became,  and  has  continued,  an 
inventor  of  electric  railway  systems  and  devices. 

Many  years  ago — /.  e.,  in  1688 — a  vessel  containing  melted 
glass  broke,  and  a  portion  of  the  fused  mass  found  its  way  be- 
neath a  large  flag-stone,  which,  when  removed,  revealed  a  plate 
of  glass.  This  accident  suggested  to  TheVart  the  idea  of  casting 
plate  glass.  Crandall,  who  obtained  fame  through  his  toy  build- 
ing blocks,  owned  a  large  glass  ball,  which  seemed  possessed 
with  life,  always  rolling  where  it  was  not  wanted.  This  was  the 
small  circumstance  which  led  to  his  invention  of  "Pigs  in 
Clover  "  by  which  he  cleared  over  $40,000. 

From  the  foregoing  facts  a  valuable  principle  is  deduced, 
namely: 

An  observation  of  the  ordinary  circumstances  of  the  day, 
with  a  view  to  invent,  assists  the  desire  and  attempts  to  invent, 
and  suggests  finally  the  basis'  of  a  new  and  useful  invention. 

Experiment  a  Teacher. — Experimenting  for  the  purpose  of 
solving  a  certain  problem  often  suggests  the  solution  of  an  inde- 
pendent and  unexpected  problem. 

Glauber  searched  long  and  diligently  for  the  Philosopher's 
Stone,  and  by  putting  certain  chemicals  together  for  this  pur- 
pose found  that  he  obtained  a  substance  radically  different  from 
either  of  the  constituents.  The  compound  thus  produced  is  the 
medicine  which  bears  his  name.  It  is  well  to  listen  thus  to  the 
dictates  of  experiment,  and  not  to  become  the  least  discouraged. 
Newton  tried  in  every  possible  way  to  solve  the  theory  he  had 
as  to  the  existence  of  gravitation.  The  natural  experiment  or 
operation  of  nature  in  the  falling  of  an  apple  taught  him  in  a 
manner  entirely  unexpected.  While  Edison  was  experiment- 
ing in  telegraphy  he  saw  some  operation  occur  in  an  experiment 
which  taught  him  a  scientific  principle  he  had  not  before  fully 
realized,  and  at  once  concluded  that  if  that  principle  were  really 
what  it  appeared,  he  would  make  a  talking  machine.  In  the 
early  days  of  printing,  the  type  was  carved  upon  wooden  blocks; 


12 

but  often  breaking  off,  new  letters  had  to  be  glued  on  to  take 
their  place.  This  taught  an  inventor,  who  was  seeking  for  im- 
provement in  the  art,  to  make  our  present  movable  type. 

Different  inventors  follow  different  paths  in  the  process  of 
inventing.  In  some  cases  they  perform  experiments  mentally 
upon  their  conceptions.  One  experiment  leads  in  their  mind 
to  another,  with  new  suggestions,  until  finally  they  are  able  to 
decide  upon  the  fact  of  the  invention  as  to  whether  it  is  opera- 
tive or  not.  This  is  the  most  economical  method.  It,  in  itself, 
trains  the  mind  to  the  power  of  intense  imagination  and  of  in- 
vention. Many  preliminary  experiments  may  often  be  dropped 
by  studying  books  on  the  subject,  to  discover  just  what  facts 
and  principles  exist  that  bear  on  the  matter  in  hand.  Many 
inventions  have  been  made  successful  upon  completion  of  the 
first  device.  A  pencil  and  piece  of  paper  will  greatly  aid  the 
imagination,  and  will  save  much  useless  experimenting.  I 
lately  visited  at  his  home  an  inventor  of  a  "  Put  a  Nickel  in  the 
Slot  and  Have  Your  Photograph  Taken."  The  machine  did  all 
the  work. ,  It  was  automatic  from  the  beginning  to  the  end  of 
the  process.  Although  marvelous  to  behold,  and  apparantly 
intricate,  it  was  the  result  of  the  very  first  experiment,  and  it 
did  its  work  not  only  well,  but  every  time.  I  found  that  it  took 
but  two  months  for  him  to  reduce  the  mental  invention  to  the 
physical;  but  to  devise  the  complete  mental  invention  and  to 
experiment  with  all  the  movements  ///  the  mind  assisted  by 
pencil  and  paper,  occupied  the  larger  portion  of  a  year. 

Some  begin  to  experiment  upon  the  very  first  conception, 
and  even  build  a  full-sized  machine  at  the  first,  and  when  the 
difficulties  are  found  another  device  is  built,  and  so  on.  This 
method  is  more  expensive  and  requires  more  time,  and  does  not 
in  itself  increase  the  power  of  imagination,  which  is  one  of  the 
greatest  aids  to  an  inventor.  A  harmonious  blending  of  these 
two  methods  makes  the  greatest  inventor. 

The  style  followed  by  the  chemist  and  physicist  in  their  ex- 
perimenting for  new  principles  is  often  copied  by  successful  in- 
ventors. The  former  use  small  and  almost  minute  quantities 
and  apparatus,  costing  very  little.  Small  experiments  are  as 
positive  and  often  more  so  than  large  experiments.  Plante  ex- 
perimented upon  his  secondary  battery  with  small  quantities  of 
chemicals,  costing  but  a  few  cents  each.  Distribute  your  time 
and  money  on  numerous  small  experiments  rather  than  upon 
a  few  large  ones. 

Reparation. — It  is  well  known  that  tons  of  zinc  have  been 
wasted  by  the  telegraph  companies  by  throwing  away  the  stubs 
of  crow-foot  zincs  used  in  batteries.  Georges  d'Infreville  has 


13 

made  an  invention  whereby  this  waste  need  not  exist.  Other 
important  inventions  could  be  quoted  to  illustrate  the  same 
teaching,  namely  : — When  a  part  of  a  machine  wears  out,  and 
must  be  thrown  away,  let  the  knowledge  thereof  be  an  incen- 
tive to  prompt  to  a  modified  construction  whereby  the  worn-out 
part  may  be  replaceable  by  a  new  part,  so  that  time  and 
material  shall  not  be  wasted.  In  some  old  instances,  a  whole 
valuable  device  was  thrown  away  until  inventions  were  made 
whereby  it  was  only  necessary  to  throw  away  that  part  which 
was  worn  out. 

Critical  Inspection  of  Crude  Devices. — Scarcely  does  an  in- 
ventor see  the  invention  of  another  but  that  it  looks  very  crude, 
•and  that  he  makes  valuable  improvements,  whereby  both  make 
more  profit  than  either  could  have  hoped  to  have  made 
alone.  The  one  has  had  practice  perhaps  in  conceiving  prolific 
ideas,  but  lacks  practice  in  making  mechanical  inventions.  He 
puts  the  crude  device  upon  the  market.  It  is  about  to  fail. 
The  second  inventor,  equipped  with  the  broad  ideas,  applies  his 
practice  obtained  in  making  mechanical  inventions  and  im- 
proves so  greatly  upon  the  crude  device  as  to  reap  benefit  in 
conjunction  with  the  first  inventor. 

A  Device  for  doing  by  Electricity  that  which  had  previously 
been  done  by  some  other  Agency. — Since  the  time  of  Cain  and 
Abel  welding  has  been  accomplished  by  hammering.  Only  in 
modern  times  has  a  successful  device  been  constructed  whereby 
not  only  can  ordinary  welding  be  accomplished  by  the  electric 
current,  but  the  device  will  weld  that  which  cannot  be  welded 
by  the  old  process.  Inventing  is  often  like  a  horse-race.  All 
the  jockeys  are  endeavoring  to  reach  the  same  goal  first,  and 
there  is  a  theoretical  possibility  that  all  will  get  there  at  the 
same  fraction  of  a  second,  but  this  scarcely  ever  happens. 
Possibly  two  arrive  instantaneously  apparently.  In  any  event, 
the  one  who  beats  is  the  one  who  receives  the  prize.  For  the  last 
decade  inventors  have  been  attempting  to  apply  electric  cur- 
rents to  welding.  The  one  who  first  applied  the  electric  con- 
verter principle  where  the  maximum  heating  current  is  obtained 
from  an  electrical  source  was  the  first  to  succeed,  but  soon 
afterwards  others  made  the  same  invention  independently. 
Other  results  are  being  sought  through  the  electric  current,  and 
inventors  should  be  awake  to  this  suggestive  idea  and  attempt 
thereby  to  widen  the  usefulness  of  electricity. 

The  successful  application  of  welding  by  electricity  is  some- 
what similar  to  the  introduction  of  the  air  brake.  Others  had 
attempted  the  solution  of  the  problem,  but  fell  short  of  success. 
Judges  Walker  and  Swayne  set  forth  in  an  important  case  (2 


14 

Bann  and  Ard.,  55,  1875),  that,  although  others  had  conceived 
the  idea  of  air  brakes  before  Westhinghouse,  yet  he  is  the  first 
legal  inventor  and  entitled  to  protection  because  the  first  to  in- 
vent a  practically  operative  air  brake,  which  is  so  important  to 
the  safety  of  human  life  and  property.  An  important  principle 
is  contained  in  the  above  illustrations.  It  is  often  more  important 
to  be  the  first  to  conceive  broad  ideas  than  to  be  first  to 
produce  the  best. 

Omission. — By  omitting  one  or  more  of  the  elements  which, 
were  at  first  thought  to  be  necessary,  but  which  one  finds  may 
be  omitted  and  the  same  or  even  better  results  obtained  by  a 
new  mode  of  operation,  an  invention  is  made.  If  by  omitting  an 
element  the  device  is  worse  than  before,  then  there  is  no  inven-  . 
tion.  A  certain  party  omitted  the  board  foundation  of  a 
Nicholson  pavement,  but  Judge  Blodgett  decided  that  these 
omissions  constituted  no  invention  ;  but  a  reconstruction  of  a 
machine  so  that  a  less  number  of  parts  will  perform  all  the 
functions  of  the  greater  is  the  invention  of  a  high  order.  In 
a  friction  clutch  for  hoisting-machines  the  patentee  dispensed 
with  one  of  the  friction  cones  and  flanges  found  in  the  prior 
art,  re-arranged  the  machine  accordingly  and  put  a  spring  where 
it  was  needed,  and  the  patent  was  upheld  by  Judge  Wheeler. 

Transposition. — An  inventor  may  often  improve  the  manufac- 
ture by  changing  the  relative  positions  of  the  parts  of  a  device  if 
at  the  same  time  he  accomplishes  the  same  or  better  results. 
Permutation  locks  have  thus  been  improved;  also  watchman's 
time  recorders.  An  inventor  made  a  new  location  of  a  hinge 
and  spring  catch  in  a  lantern  and  remedied  a  great  difficulty  in 
manufacture  and  use,  and  its  advantages  were  immediately 
recognized  and  other  manufacturers  began  to  copy.  The  patent 
was  upheld  by  Judge  Wallace. 

Change  of  Form.— Construct  one  or  more  of  the  parts  of 
such  a  form  or  shape  that  an  otherwise  essential  feature  may  be 
omitted.  One  by  the  name  of  Russell  modified  a  water  pump 
by  constructing  the  inwardly  projecting  flange  of  such  a  form 
that  it  could  be  used  wholly  for  the  base  of  the  pump,  and  thus 
do  away  with  any  frame-work.  His  patent  for  this  improvement 
was  upheld  by  Judge  Colt. 

By  a  mere  change  of  form  a  new  result  is  often  obtainable. 
A  patented  baby-jumper  differed  from  other  jumpers  in  a  back- 
ward curvature  of  the  suspension  rod  to  prevent  contact  with 
the  child,  and  this  improvement  in  mere  form  was  held  patent- 
able  by  Judge  Blodgett.  The  manufacture  was  as  cheap  as  with- 
out the  curvature,  but  as  the  result  was  improved  with  the 
change  of  form,  more  was  obtained  for  the  same  money. 


15 

A  similar  case  is  that  of  a  carbon  filament  for  incandescent 
lamps  being  made  with  a  curve  like  a  horseshoe,  instead  of 
straight.  They  are  equally  cheap  to  make  and  they  possess  the 
improved  result  or  advantage  of  having  the  leading-in  wires 
enter  the  same  end  of  the  lamp  bulb,  and  of  exposing  more 
illuminating  surface  per  volume  of  vacuum  space. 

Combined  Inventions. — An  inventor  may  often  obtain  inven- 
tion by  combining  the  merits  of  two  or  more  devices  into  one.  If 
the  result  is  an  invention  of  equal  convenience,  cheaper  than 
both  elements  and  as  meritorious  as  both,  the  single  invention 
is  a  true  invention  according  to  Judge  Lowell. 

As  an  illustration,  the  preserving  of  meat  may  be  taken. 
Enveloping  meat  in  a  covering  of  fibrous  or  woven  material  is 
old.  Subjecting  the  meat  to  the  action  of  a  current  of  air  of 
suitably  low  or  regulated  temperature  is  also  old.  Combining 
the  two  elements  is  pronounced  new  and  patentable  by  Judge 
Nixon.  • 


CHAPTER  VII. 
THE  INITIAL    STEP. 


IT  is  not  enough  to  have  a  love  for  inventing.  You  may  ad- 
mire other  inventors  and  inventions,  and  may  think  how  satis- 
fied and  prosperous  you  might  be  if  you  could  make  a  success, 
and  you  may  even  realize  some  problems  which  need  solving, 
and  yet  not  be  an  inventor.  More  is  needed  than  mere  desire. 
In  order  to  get  there,  one  step  must  be  taken  at  a  time.  What, 
therefore,  is  the  first  step  ? 

An  inventor  deals  with  positive  results  and  absolute  condi- 
tions, and  not  with  chaos  and  creation.  He  proceeds  in  a  man- 
ner peculiar  to  itself,  and  not  in  a  common  way  with  other 
workers.  Mathematicians,  physicists,  chemists,  carry  out  con- 
ditions, and  obtain  a  result ;  and  the  fulfilment  of  the  same  con- 
ditions always  produces  the  same  result;  2X3X4  always  equals 
24.  There  is  positively  no  exception.  The  physicist  follows 
the  same  law.  If  he  wishes  to  transfer  electricity  from  one 
point  to  another  he  must  fulfil  the  proper  conditions.  An  elec- 
tric current  of  about  two  volts  always  decomposes  water  into 
hydrogen  and  oxygen  gases.  The  result  is  sure  to  come,  and 
there  is  but  the  same  result. 

With  the  inventor  everything  is  just  the  opposite.  His 
given  quantity  is  the  result,  while  the  unknown  quantities  are 


16 

the  conditions.      In  the  above  arithmetical  problem  his  known 
quantity  corresponds   to    24,  and  it  is  to  find  the  conditions 
which,  when  obeyed,  will  give  24.      It  is  evident  that  the  result 
might  be  obtained  in  many  independent  ways  ;  thus 
2X3X4  equals  24 
6X3+1+5  "     24 
30 — 6    "     24 
(2X6)+  (6X2)    "     24 

and  so  on  indefinitely,  and  limited  only  by  the  capacity,  and' 
patience  of  the  mathematican.  Does  it  not  follow,  therefore,  that 
an  invention  has  different  answers,  and  that  a  problem  in  arith- 
metic has  only  one  answer  ?  Yes  !  this  is  the  general  rule.  The 
product  24  may  be  obtained  by  carrying  out  many  conditions, 
or  by  few.  1  +  1  +  1  +  1,  etc.,  will  eventually  result  in  24  as  the 
answer,  or  simply  2X12  =  24.  The  inventor  should  aim  for  the 
fewest  conditions.  The  result  should  be  obtained  by  as  few 
steps  as  possible. 

Analysis. — The  result  sought  is  usually  compound,  not  ele- 
mental. There  is  scarcely  an  exception  to  this,  although  before 
the  trouble  is  taken  to  analyze  it  the  result  seems  elemental 
and  not  compound.  The  first  essential  step  consists  in  analyz- 
ing the  problem  into  two  elements  and  if  possible  into  more 
than  two.  Each  element  may  itself  be  a  compound.  This  analy- 
sis is  exceedingly  important,  and  will  aid  in  systematic  work. 
Nothing  is  more  important  in  inventing  than  to  have  a  target. 
He  who  has  a  definite  aim  is  the  one  who  conquers. 

To  illustrate  the  point,  let  an  example  be  taken — e.  g.,  the  type- 
writer— $20  on  every  Remington  typewriter  sold  are  said  to  go  to 
the  inventor.  The  claims  cover  only  the  particular  construction  of 
the  machine,  the  elementary  ideas  being  public  property.  Sup- 
pose it  is  desired  to  invent  a  radically  different  typewriter  from 
the  Remington  or  any  other  form  found  in  practice.  The  initial 
step  is  to  analyze  the  problem. 

The  following  example  will  serve  to  illustrate  how  a  result 
is  divisible  into  its  elements: 

i.  The  general  result  is  a  machine  which  will  write  or 
print  words  and  sentences  when  properly  controlled  by  an 
operator. 

_The  elementary  results  are  (a)  means  for  making  the  type  to 
strike  the  paper  at  proper  intervals  of  space  ;  (b)  means  for 
moving  the  paper  through  the  proper  space  after  each  letter  is 
printed;  (c)  means  for  being  able  to  see  the  printing  during 
the  operation,  as  in  handwriting;  (d)  means  for  retracting  the  pa- 
per when  a  mistake  is  made;  (e)  means  for  making,  simultaneously, 
multiple  copies  of  the  printed  matter;  (f)  means  for  moving  the 


17 

paper  at  the  end  of  each  line;  (g)  means  for  giving  a  signal 
near  the  end  of  each  line;  (h)  means  for  easily  replacing  a 
filled  sheet  by  a  new  sheet;  (i)  means  for  adjusting  the  machine 
to  print  the  lines  at  any  approximately  desired  distance  apart; 
(j)  means  for  beginning  the  lines'  at  a  given  margin;  and  (k) 
means  for  printing  both  capitals  and  small  letters,  figures,  and 
punctuation  marks,  and  possibly  for  printing  French,  German, 
or  some  other  language  besides  English.  By  this  analysis 
a  complex  problem  is  divided  into  eleven  independent 
simple  problems,  which  upon  further  consideration  may  be 
found  divisible.  The  power  of  analyzing  results  comes  by 
practice.  Sometimes  the  inventor  needs  to  obtain  a  new  result — 
/.  e.,  doing  something  which  no  one  ever  thought  of  doing. 
Here,  also,  the  first  step  is  analysis.  One  who  wishes  to  train 
to  be  an  inventor  or  to  improve  his  qualifications  will  find 
it  profitable,  just  for  the  practice  alone,  to  take  a  new  or  old  re- 
sult and  try  to  divide  it  up  into  as  many  sub-results  as 
possible. 

The  practice  in  analyzing  should  be: 

1.  Gradual. — Do  not  begin  with  intricate  problems.     What 
would  be  thought  of  an  architect  who  tries  to  design  a  palace 
before    he    can    design    a    cottage  ?     Begin    on    the   simplest 
problem  and  then  pass  to  the  greater  and  more  complex  prob- 
lems. 

2.  Continuous. — Some  men  are  very  enthusiastic  at  intervals 
in  any  given  undertaking  and  at  alternate  intervals  lose  their  in- 
terest.    They  are  early  and  late  at  work  upon  their  scheme,  and 
just  as  they  are  thoroughly  saturated  with  the  subject  and  prob- 
ably near  success  they  allow  their  mind   to   be  transferred  to 
some  other  subject,  forgetting  the  former  until  it  is  too  late. 
Recreation  is   good   and  should   be  practiced,  but   a  loss  of 
enthusiasm  should  not  be  allowed.     Continually  maintain  the 
spirit  of  intense  thought,  stopping  only  for  recreation  and  other 
matters  of  business,  taking  up  the  practice  again  with  renewed 
enthusiasm. 

3.  Special. — The  inventor  should  confine  himself,  not  to  a 
special  device,  but  to  that  department  of  invention  in  which  is 
to  be  employed  his  special  knowledge  and  experience.     Thus 
a  mechanic  can  do  better  in  analyzing  problems  bearing  upon 
the   particular   mechanical   device    for   carrying   out  a   broad 
scientific  invention  than  in  conceiving  a  plan  for  multiplex  tele- 
phony.    When  he  understands  the  principles  of  the   multiplex 
telephony    he  can  then  analyze  the  problem  of  obtaining  the 
same  results  by  less  movements,  or  fewer  parts,  or  in  a  radically 
different  manner,  leaving  the  system  comparatively   worthless 


18 

without  the  use  of  his  improvements.  On  the  other  hand, 
scholars  and  professors,  having  a  broad  knowledge  of  all  things, 
do  not  need  to  practice  analysis  on  mechanical  problems,  but 
those  relating  to  methods,  chemicals,  systems,  and  to  the  ac- 
complishing of  new  results.  The  ordinary  manufacturer, 
partly  learned  and  partly  a  mechanic  and  partly  a  business  man, 
may  practice  by  analyzing  medium  problems,  getting  additional 
assistance  from  the  mechanic,  the  professor,  or  books. 

Varied. — There  is  a  sense,  though,  where  practice  should  be. 
varied.  One  is  apt  to  dwell  upon  improvements  of  the  devices  he 
daily  meets  with.  This  makes  for  him  a  very  narrow  field.  He 
does  not  get  a  sufficiently  varied  practice.  He  should  endeavor 
to  broaden  his  knowledge  through  books  and  other  sources  of 
knowledge.  A  man  occupied  in  business  is  apt  to  make  inventions 
relating  to  stationery,  ink  bottles,  blotting  pads,  fountain  pens, 
&c.,  whereas  his  evenings  and  spare  time  could  be  occupied  with 
the  exhaustive  study  of  some  particular  and  newer  department  of 
science  or  industry  than  that  which  occupied  the  attention  of 
the  scribes  in  the  year  i.  Let  the  problem,  therefore,  relate  to 
something  special,  but  do  not  narrow  it  to  the  small  number  of 
devices  you  are  apt  to  meet  day  after  day  and  year  after  year  in 
your  routine  of  employment. 


CHAPTER    VIII. 

MAKING  AND  DEVELOPING  MECHANICAL  INVENTIONS. 


FROM  a  study  of  inventions  I  establish  the  proverb  that  a 
problem  known  is  a  problem  half  solved.  The  only  exception 
is  the  case  where  natural  laws  prevent.  An  old  problem,  mean- 
ing the  same  thing  by  opposites,  is  that  a  double-minded  man  is 
unstable  in  all  his  ways.  The  problem  must  be  known.  It  must  not 
be  simply  a  vision,  an  indefinite  difficulty  to  be  overcome,  but  it 
must  be  analyzed.  The  next  step — the  conception — is  the  mental 
doing  of  something  in  order  to  get  one  of  the  elemental  results; 
and  then  doing  something  else  to  get  the  second  elemental  re- 
sult ;  and  so  on,  until  each  elemental  result  is  accomplished  in 
the  mind.  This  will  be  found  to  be  the  easiest  part  of  inventing. 
The  invention  will  be  very  crude  at  first.  It  will  be  very  im- 
practicable, and  perhaps  so  intricate  and  complex  as  to  lead  to 
discouragement.  Do  not  expect  to  get  at  once  the  best  way 
of  obtaining  the  result.  This  has  never  been  the  rule  with  other 


19 

inventors.  The  first  form  of  mental  device  is  crude.  Out  of 
ten  men  having  sufficient  knowledge,  and  working  for  the  same 
solvable  result,  there  will  scarcely  be  one  but  will  devise  some 
mental  invention  for  obtaining  the  result.  In  order  to  arrive 
quickest  at  the  simplest  solution  one  should  travel  by  guide- 
boards,  which  themselves  will  not  serve  as  horses  to  carry  him 
to  his  destination  and  thereby  relieve  him  of  the  tedious  walk 
and  work,  but  they  will  be  so  useful  that  if  they  were  not  there 
he  would  have  to  guess  the  way.  What  are  the  guides  which 
will  serve  to  make  the  simplest  conception  come  the  quickest  ? 
They  are  given  in  the  case  below  regarding  the  arc  lamp. 

The  developing  process  depends  upon  the  class  to  which  the 
proposed  invention  belongs.  All  inventions,  fortunately,  are 
found  to  be  divisible  into  two  classes,  for  purposes  of  develop- 
ment— Mechanical  and  Scientific,  and  each  of  these  into — 

KINETIC  AND  STATIC. — Samples  of  the  former  are  the  printing 
press,  typewriter,  cotton-gin,  phonograph,  annunciator,  harvest- 
ing machine,  and  spinning  jenny  ;  and  of  the  latter  are  cars, 
buildings,  aqueducts,  steam  boilers,  certain  tools,  etc. 

The  distinction  is  this  :  Kinetic — meaning,  literally,  relating 
to  motion — describes  all  those  inventions  in  which  the  elemental 
results  or  steps  of  the  problem  are  carried  out  by  elemental 
motions,  and  the  whole  problem  by  a  combination  of  motions. 
Static — meaning  the  reverse  of  motory — is  a  term  which  in- 
cludes all  those  inventions  in  which  the  results  are  accomplished 
by  a  combination  of  stationary  elements,  varying  in  form  and 
number,  and  bearing  certain  fixed  relations  to  each  other.  It 
includes  all  devices  and  products  in  which  motion  is  not  one  of 
the  essential  elements. 

KINETIC  INVENTIONS. — Comprehension  in  the  abstract  is  diffi- 
cult; therefore  let  an  example  be  considered.  Among  the  best  is 
the  arc  lamp.  Let  it  be  supposed  that  the  arc  lamp  is  capable  of 
simplification,  that  it  has  not  yet  reached  its  simplest  form.  The 
initial  step,  as  by  the  preceding  chapter,  is  to  analyze  the  result. 

General  Result. — The  general  result  is  to  produce  a  combina- 
tion of  motions  which  will  result  in  the  production  of  an  elec- 
tric spark  of  constant  length.  Every  problem  in  kinetic  in- 
vention is  to  produce  a  combination  of  motions  in  order  to  ob- 
tain the  final  result.  Knowledge,  obtained  by  the  experience  of 
others,  furnishes  us  with  the  fundamental  and  necessary  infor- 
mation, that  the  heat  of  the  arc  burns  the  carbons  away,  so  that 
the  spark  tends  to  grow  longer. 

First  Elemental  Result. — The  first  motion  of  the  carbon  or 
carbons,  in  order  that  the  spark  may  exist,  is  that  they  should 
either  be  brought  together  and  moved  away  ;  or,  if  already  in 


20 

contact  normally,  to  be  moved  away  from  each  other  to  such  a 
distance  as  to  produce  the  predetermined  length  of  arc.  Decide 
upon  the  simpler  of  the  two.  Let  it  be  supposed  that  they  are 
in  contact  normally.  The  first  result  to  be  obtained,  therefore, 
is  to  produce  such  a  motion  that  the  distance  between  the  car- 
bons may  quickly  increase  from  zero  to  maximum,  and  remain 
at  maximum  or  a  little  under  maximum.  The  following  ques- 
tions present  themselves:  Shall  the  motion  be  rectilinear,  curvi- 
linear, vibratory,  circular,  or  elliptical  or  a  combination  of  two- 
or  more  of  the  above  ?  In  the  present  problem  this  question 
is  to  be  answered  by  the  inventor. 

First  Elemental  Invention. — Enumerate  in  the  mind,  or  on 
paper,  all  the  different  ways  in  which  the  distance  between  two 
masses  may  be  increased.  It  is  true  too  often  that  the  first  device 
is  crude  because  the  inventor  did  not  stop  to  consider  several  ways, 
and  choose  the  best.  The  different  sources  of  power  are  fur- 
nished by  knowledge,  and  are  to  be  enumerated  in  each  ele- 
mental invention.  These  primary  forces,  with  their  modifica- 
tions, are  heat,  light,  magnetism,  electricity,  gravitation,  chem- 
ical action,  contraction,  weights,  wound-up  springs, 
explosions,  tides,  waves,  wind,  earth's  magnetism  and  currents, 
cohesion,  adhesion,  pressure,  primary  and  secondary  batteries, 
thermopiles,  electric,  steam,  vapor,  gas  and  other  motors,  and 
combinations  of  two  or  more  of  the  above.  In  every  elemental 
invention  these  sources  of  power  should  be  considered  and  the 
best,  single  or  combined,  chosen.  The  means  for  communi- 
cating, or  changing  the  direction,  or  varying  the  source  of 
power,  should  also  be  chosen  from  an  enumerated  list.  To- 
gether with  their  modifications,  they  are,  in  part,  the  lever, 
screw,  wedge  or  inclined,  plane,  pulley  or  wheel,  smooth  or 
toothed,  belt,  magnet  and  armature,  compound  lever,  pawl 
and  ratchet,  crank,  mediums,  such  as  gas  and  liquid,  cam, 
tackle,  wheel  and  axle,  worm  gearing,  bevel  gearing,  escape- 
ment, frictional  gearing,  idle-wheel  gearing,  pendulum, 
toggle  joint,  and  parallel-motion  device.  The  first  elemental 
invention  consists  in  combining  one  or  more  of  the  above 
sources  of  power  with  one  or  more  of  the  above  means  for 
communicating  and  directing  the  power,  until  that  combination 
is  obtained  which  is  the  best  in  the  opinion  of  the  inventor. 
To  be  sure,  this  is  a  tedious  and  lengthy  operation,  but  there  is 
no  short  road  for  the  inventor.  He  must  follow  the  guides  and 
be  willing  to  plod  his  way.  If  there  are  ten  means  of  com- 
municating power  the  number  of  possible  combinations  is  in 
the  thousands.  How  improbable,  therefore,  is  it  for  one  to 
"  hit "  upon  a  thing  ?  It  is  possible,  but  not  probable. 


21 

Second  Elemental  Result. — If  the  lamp  is  for  ordinary  use, 
one  carbon  may  remain  stationary  and  the  other  fed.  If  for  a 
focus  lamp  in  locomotives  or  magic  lanterns,  both  carbons 
should  be  fed.  The  questions  which  should  be  asked,  as  in 
similar  kinetic  inventions,  are:  Shall  the  carbons  move  simul- 
taneously or  alternately;  in  a  linear  or  curvilinear  direction; 
with  uniform  rates,  continuously,  or  intermittently,  or  vibratingly; 
fast  or  slowly;  by  independent  sources  of  power  or  jointly  by 
the  same  power,  or  with  a  combination  of  two  or  more  of  those 
motions? 

Second  Elemental  Invention. — In  order  to  give  both  carbons 
the  proper  motion  the  same  steps  in  combination  should  be  fol- 
lowed as  in  the  first  elemental'  invention,  remembering  the  fact 
that  one  of  the  carbons  is  consumed  about  twice  as  fast  as 
the  other. 

Third  Elemental  Result. — The  mechanism  obtained  by  the 
former  step  is  useless  without  means  of  regulation.  In  numer- 
ous devices  in  other  departments  of  industry  regulating 
mechanisms  are  required.  The  same  principle  of  invention 
which  applies  to  the  one  applies  to  the  other.  What  is  the 
exact  meaning  of  regulation  as  being  a  result?  What  object 
must  be  accomplished?  The  mechanism  obtained  by  the 
second  elemental  invention  does  not  act  uniformly  with  the  con- 
sumption of  the  carbons.  If  the  carbons  burn  away  so  fast 
that  the  arc  distance  increases,  the  mechanism  should  hasten 
the  speed  of  the  carbons,  and  vice  versa. 

Third  Elemental  Invention. — What  force  shall  be  used  to 
regulate?  The  force  which  causes  the  irregularity.  This  is 
found  to  be  true  in  other  regulators.  In  the  steam  engine  the 
load  or  power  with  which  the  mechanism  moves  is  the  regu- 
lating power  for  operating  the  governor.  This  is  equivalent  to 
saying  that  the  steam  pressure  is  the  force  which  regulates  the 
flow  of  the  steam  through  the  throttle.  In  the  dynamo  regu- 
lator the  increase  and  decrease  of  current  are  the  regulating 
power,  and  so  in  arc  lamps,  the  regulating  power  is  the  variation 
of  the  current  by  the  medium  of  a  magnet.  This  rule  is  gen- 
eral, not  absolute;  therefore  it  is  necessary  to  consider  if  the 
regulation  can  be  effected  by  other  sources  of  power.  Having 
decided  what  source  to  employ,  the  point  of  application  of  the 
power  should  be  considered.  As  many  points  as  possible 
should  be  reviewed.  In  a  clock  it  is  sometimes  applied  to  an 
escapement,  while  in  an  electric-clock  system  it  is  applied  to  a 
central  clock  once  a  minute  or  once  an  hour,  and  thereby  all 
the  clocks  are  regulated.  In  the  same  manner  much  tedious 
labor  must  be  exercised  in  enumerating  the  various  regulators 


22 

in  other  departments  of  industry  in  order  to  suggest  to  the  mind 
the  possible  and  preferable  point  of  application  of  the  power. 

The  Last  Elemental  Result  and  Invention. — Before  combining 
elemental  inventions  to  form  the  general  one  sought,  some  new 
and  additional  result  should  be  considered,  whether  this  is  a 
problem  of  the  arc  lamp  or  not.  At  a  certain  stage  of  the  arc 
lamp  industry  it  was  necessary  to  switch  off  the  lamp,  and 
throw  in  the  main  line  by  a  hand  switch,  and  therefore  the 
automatic  cut-out  was  invented,  which,  however,  is  now  expired 
as  to  the  patent.  In  inventing  there  should  be  considered  any 
additional  results  over  the  usual  results.  They  may  consist  in 
certain  attachments  or  in  that  portion  of  the  invention  relating 
to  static  invention. 

Consideration  of  other  devices  in  a  similar  manner  will  up- 
hold the  principle  of  invention  that  kinetic  mechanical  inventing 
consists  in  combining  those  elementary  or  compound  motions 
which  are  adapted  to  produce  the  results  sought.  This  is  the 
secret,  and  it  involves  and  necessitates  preliminary  practice  and 
preparation  before  the  inventor  can  expect  to  solve  any  very  in- 
tricate problem. 

Motions. — It  is  fortunate  that  the  inventor  is  not  obliged  to 
discover  motions.  These  are  very  old,  although  every  inventor 
may  not  know  them  or  cannot  call  them  to  mind  at  will.  No 
new  elementary  motion  has  been  discovered  for  many  years  ; 
but  the  inventor  has  combined  and  re-combined  them  with  such 
wonderful  results  as  to  make  all  the  classes  of  machinery  at 
present  known.  The  number  of  combinations  of  the  present 
known  motions  is  in  the  thousands. 

The  inventor  must  know  the  known  motions  before  he  can 
expect  to  make  any  headway;  further,  he  should  know  them  by 
heart,  and  should  experiment  in  their  combination  for  the  solu- 
tion of  problems,  whether  important  or  not,  and  he  should 
analyze  important  kinetic  mechanical  inventions.  The  more 
important  elementary  and  compound  motions  are  given  and  ex- 
plained below. 

In  the  first  place,  all  motion  is  relative — not  absolute — be- 
cause no  absolutely  stationary  particle  exists  as  far  as  known. 
All  things  on  the  earth  move  because  the  earth  itself  moves.  Also, 
the  molecules  of  a  body  are  always  in  vibratory  motion.  For 
the  purposes  of  the  inventor,  the  earth  may  be  assumed  to  be 
fixed,  and  that  motion  is  to  be  considered  relatively  to  the 
assumed  stationary  earth,  or  to  movable  or  fixed  points  or 
objects  upon  the  earth. 

The  shortest  distance  between  two  points  is  a  straight  line. 
A  particle  may  move  in  that  line,  and  in  so  doing  has  rectilinear 


23 

motion,  the  simplest  motion  known,  and,  in  short,  the  only 
elementary  motion  known.  Another  very  simple  motion 
is  curvilinear  motion,  but  when  resolved  is  found  to  consist 
of  two  rectilinear  motions  occurring  or  at  least  tending  to  occur 
simultaneously  at  the  same  time.  This  principle  of  motion  is 
beautifully  illustrated  by  the  writing  telegraph,  using  two  inde- 
pendent currents.  The  motion  of  the  hand  to  make  a  hori- 
zontal rectilinear  line  gradually  increases  the  strength  of  a 
distant  magnet  by  means  of  a  delicate  rheostat.  The  motion  of 
the  hand  to  make  a  rectilinear  line  perpendicular  to  the  first 
increases  the  strength  of  a  second  distant  magnet  near  the  first 
and  perpendicular  to  the  same.  Each'  magnet's  armature  is 
pivoted  to  and  moves  a  common  pencil.  Whatever  the  motion 
of  the  hand  (rectilinear  or  curvilinear),  the  magnets  cause  the 
pencil  to  have  the  same  motion,  and  yet  the  armature  of  each 
magnet  can  move  in  a  rectilinear  line  only.  The  pencil  par- 
takes of  the  combined  motion  of  the  two  armatures  whenever  a 
slanting  or  curved  line  is  formed.  If  the  hand  moves  in  an 
ellipse,  the  pencil,  moved  by  the  magnets,  moves  in  an  ellipse, 
and  so  on  for  every  motion.  The  pencil  sometimes  has  rectili- 
near and  sometimes  curvilinear,  but  the  armatures  always  have 
rectilinear  motion.  A  curved  motion  is  therefore  a  combination 
of  rectilinear  motions. 

The  simplest  form  of  curvilinear  motion  occurs  when  a  body 
has  circular  motion.  The  body,  while  in  motion,  remains  equally 
distant  from  a  fixed  point.  Parabolic  motion  is  that  in  which 
the  body  moves  simultaneously  in  two  directions  at  right  angles 
to  each  other,  with  velocities  which  are  respectively  accelerating 
and  constant,  the  accelerating  increasing  as  the  square  of  the 
distance.  Other  forms  of  curvilinear  motion  are  elliptical, 
sinusoidal,  being  in  that  curve  assumed  by  a  flexible  cord  sus- 
pended loosely  and  having  its  ends  attached  to  two  fixed  hori- 
zontally located  points  ;  spiral,  being  in  a  curve,  having  the 
appearance  of  a  snake  coiled  upon  the  ground  or  like  the  spring 
in  a  watch;  helical,  being  in  a  curve  represented  by  the  ordinary 
helical  spring;  hyperbolical,  to  the  eye  apparently  like  the  para- 
bolical, the  curve  of  the  hyperbola  being  obtainable  by  the 
intersection  of  a  conical  surface  by  a  plane  parallel  to  the  axis 
of  the  cone;  epicycloidal,  being  the  motion  of  any  given  particle 
in  the  circumference  of  a  wheel  when  that  wheel  rolls  either 
upon  the  outer  or  inner  side  of  a  circular  line;  cycloidal,  being 
in  that  curve  formed  by  a  point  in  the  circumference  of  a  wheel 
rolling  upon  a  straight  line  and  remaining  in  a  given  plane; 
curtate-cycloidal,  similar  to  above,  except  that  the  moving  point 
is  upon  a  projection  extending  externally  to  the  circumference  ; 


24 

and  prolate-cycloidal,  being  the  same  as  in  the  above  case,  ex- 
cept that  the  moving  point  is  attached  to  the  wheel  within  its 
circumference. 

Curved  or  rectilinear  motions  are  divisible  into  intermittent, 
continuous,  accelerating,  diminishing,  alternately  accelerating 
and  diminishing,  rapid,  slow,  gradually  accelerating  or  diminish- 
ing, reciprocating,  f.  <?.,  first  in  one  direction  and  then  in  the 
other,  and  abruptly  accelerating  or  diminishing,  and  periodical, 
being  that  motion  in  which  the  object  moves  for  a  while  and 
then  stops  for  a  while,  and  then  moves,  &c.,  differing  from  in- 
termittent motion  in  that  the  periods  of  motion  are  definitely 
durable  and  not  apparently  instantaneous.  Parallel  motion  is 
that  in  which  a  point  moves  in  a  straight  line  parallel  to  a  given 
straight  line.  Sun  and  planet  motion  is  that  in  which  one  wheel 
rolls  upon  another  which  rotates  upon  a  fixed  axis. 

Something  should  be  said  in  regard  to  the  nature  of  the  com- 
bination of  the  motions  for  producing  an  invention.  Is  it  like  a 
chemical  combination  where  the  compound  is  different  from  any 
of  its  constitutents,  or  is  it  like  a  mixture  where  the  elements  of 
the  mixture  retain  their  individual  properties  ?  It  is  sometimes 
analogous  to  the  compound  and  sometimes  to  the  mixture.  The 
curvilinear  motion  is  similar  to  the  compound,  because  the  recti- 
linear motions  in  the  curved  line  are  infinitesimally  small,  and 
can  practically  be  said  not  to  exist.  Practically  the  curvilinear 
motion  is  that  in  which  its  constitutents  lose  their  indentity  un- 
til analyzed,  as  in  the  case  of  a  chemical  compound.  In  the  steam 
engine  such  a  compound  motion  is  found  where  the  crank-pin 
moves  with  a  circular  motion.  This  circular  motion  is  combined 
with  the  motion  of  the  other  parts  of  the  engine,  not  as  in  a 
compound,  but  as  in  a  mixture.  Thus  the  eccentric,  governor 
and  slide  valve  have  motions  which  taken  together  are  essential 
parts  of  the  invention,  and  yet  they  are  as  distinct  as  if  each 
were  a  distinct  device.  The  word  "  combined  "  therefore  is  a 
general  word  in  the  science  of  inventing,  indicating  either  an 
intimate  union  or  a  mere  mixture  of  motions. 

Analysis  of  the  Motions  of  Kinetic  Mechanical  Inventions. — 
Another  analogy  exists  between  invention  and  chemistry.  The 
student  in  both  cases  becomes  better  prepared  to  solve  problems 
of  a  certain  class  by  analyzing  existing  combinations.  By  un- 
derstanding the  analyzing  of  chemical  compounds  of  a  certain 
class  he  is  better  prepared  to  obtain  a  new  compound  by  com- 
bining chemicals  ;  so  also,  by  becoming  expert  in  the  analysis  of 
an  invention  in  the  class  of  kinetic  mechanical  inventions,  he  is 
better  able  to  solve  a  given  problem  in  this  class  by  combining 
the  proper  motions.  A  few  examples  are  given,  not  only  for 


25 

such  practice,  but  to  illustrate  the  above-stated  principles  of 
inventing. 

Sewing  Machine. — One  part  of  the  thread  must  pass  through 
the  cloth  in  one  direction,  and  a  contiguous  portion  of  the 
thread  must  return  through  the  cloth  in  an  opposite  direction. 
The  motion  which  is  given  therefore  to  the  thread  is  reciprocat- 
ing if  it  is  desired  to  imitate  sewing  by  hand.  If  the  machine 
is  to  be  operated  by  the  foot,  another  motion — that  of  the 
treadle — is  also  reciprocating.  After  the  thread  is  passed 
through  the  cloth  some  motion  is  necessary  in  order  to  prevent 
some  of  that  portion  which  has  passed  through  from  returning, 
or  else  no  stitch  will  be  formed.  This  motion  is  different  in 
different  machines,  and  this  feature  admits  of  fertility  of  combi- 
nations. In  general,  the  motion  is  such  as  to  tie  a  knot  in  the 
thread,  which  serves  the  same  purpose  as  a  rivet  head  in  the 
manufacture  of  sheet-iron  articles.  When  the  thread  comes 
through  sufficiently  far  a  loop  is  formed.  In  one  type  of 
machine  two  peculiarly  shaped  prongs,  somewhat  like  the  fans 
of  an  electric  motor,  are  mounted  upon  a  rotating  shaft,  except 
that  they  are  pointed.  The  prongs  enter  the  loops  and  release 
them  at  such  relative  times  as  to  be  ready  to  form  knots  which 
are  so  artistic  in  appearance  as  to  be  used  often  for  embroider- 
.  ing.  It  should  be  said  that  this  rotary  motion  is  coupled  with  a 
reciprocating  finger,  which  acts  at  right  angles  to  the  motion  of 
the  prongs,  and  reciprocates  at  such  relative  times  as  to  assist 
the  prongs  in  forming  the  knots.  It  is  well  known  that  sailors 
can  tie  many  different  knots,  and  similarly  the  motions  and 
relative  motions  for  tying  the  knots  in  the  thread  may  continue 
to  change  until  all  the  kinds  of  knots  are  exhausted,  and  the 
motions  may  vary  in  different  machines  for  producing  the  same 
knot.  In  another  type  of  machine  two  threads  are  employed, 
and  the  motions  are  such  as  to  intertwist  or  intertie  the  two. 
Another  important  motion  is  necessary  in  a  sewing  machine.  It 
is  a  periodical  motion  of  the  cloth,  which  is  moved  the  length  of 
a  stitch  and  which  is  held  fixed  for  an  instant  at  every  stitch. 
This  motion  could  be  made  by  the  hands  of  the  sewer,  but  the 
motion  would  be  defective  ;  it  should  be  automatic.  Another 
motion  is  also  periodical,  being  that  which  feeds  the  thread  to 
the  needle  combined  with  a  friction  device  for  holding  the 
thread  at  any  desired  tension.  These  motions  are  all  derived  from 
the  reciprocating  motion  of  the  foot.  This  reciprocating  motion  is 
converted  into  rotary  motion  of  a  shaft,  which  corresponds  there- 
fore to  the  shaft  of  a  machine  shop,  by  means  of  which  different 
machines,  as  the  lathe,  planing  machine,  drill,  gear  cutter,  &c., 
may  be  operated.  In  the  sewing  machine  each  one  of  the 


motions  desired  is  likewise  obtained  by  mechanical  connection 
with  this  shaft. 

dock. — The  day  is  divided  into  24  hours,  each  hour  into  60 
minutes,  and  each  minute  into  60  seconds.  One  hand  indicates 
the  hours;  one  the  minutes,  and  one  the  seconds.  The  three 
hands  have  rotary  motions,  with  different  but  uniform  motions, 
sometimes  about  different  axes  and  sometimes  about  the  same. 
In  some  the  source  of  motion  is  circular,  as  in  the  wound-up 
main-spring,  and  sometimes  rectilinear,  as  in  the  wound-up 
weight.  Again  the  primary  motion  may  be  reciprocating  as  in 
the  case  of  a  magnet  and  its  armature.  In  all  cases,  the  primary 
motion  is  generally  immediately  turned  into  rotary  motion  of  a 
shaft  or  arbor  from  which  the  other  motions  are  derived.  This 
motion  is  true  in  a  large  class  of  kinetic  mechanical  inventions; 
the  primary  motion  is  first  converted  into  a  continuous  rotary 
motion  of  a  shaft.  The  motions  of  each  hand  of  the  clock  must 
be  so  uniform  as  not  to  vary  a  second  if  possible  during  a  year; 
but  of  course  this  is  impossible.  The  primary  motion  is 
generally  a  very  powerful  motion  and  tends  to  feed  itself  out 
in  a  few  seconds.  Therefore  it  must  be  checked,  and  allowed 
to  feed  out  intermittently;  a  little  each  instant,  as  is  generally 
done  by  an  escapement  or  balance  wheel.  The  expansions  and 
contractions  of  the  pendulum  by  heat  are  periodical  motions, 
which  cause  variations  of  velocity  of  the  hands,  whereby  the 
wrong  time  would  be  indicated,  except  by  automatic  motions  of 
contrary  direction,  which  will  neutralize  those  of  expansion  and 
contraction.  The  pendulum  is  maintained  of  the  same  actual 
length  between  the  point  of  suspension  and  the  center  of  the 
pendulum  bysuch  an  arrangement  that  the  expansions  of  certain 
parts  of  the  pendulum  cause  them  to  shorten,  while  expansions 
of  other  parts  cause  them  to  lengthen,  whereby  the  average  is  a 
non-variation  of  its  length.  Contractions  by  cold  similarly  have 
no  actual  effect  upon  its  length.  Since  the  hands  must  have 
different  relative  velocities,  the  wheels  which  gear  with  one 
another  must  be  of  proportionally  different  diameters,  the  rule 
being  that  when  two  circles  of  different  diameters  are  geared 
together  the  smaller  will  make  complete  turns  as  much  oftener 
as  it  is  smaller  in  diameter. 

Adding  Machine. — In  this,  the  figures  o,  i,  2,  3,  4,  5,  6,  7,  8, 
9  are  moved  to  distances  proportional  to  the  distances  repre- 
sented by  the  numbers  themselves.  A  series  of  wheels  will 
accordingly,  by  proper  gearing  or  lever  connections,  move 
corresponding  distances.  In  order  that  these  wheels  may  not 
move  back  again  with  the  figures  (which  must  return  to  their 
original  positions  to  be  ready  for  a  second,  third,  &c.,  move- 


ment),  the  ordinary  pawl  and  ratchet  are  usually  employed. 
The  sum  of  the  distances  moved  through  by  index  hands  on 
the  wheels  will  be  equal  to  the  sum  of  the  particular  figures 
which  were  moved  in  the  first  place. 


CHAPTER     IX. 
MAKING  AND  DEVELOPING  SCIENTIFIC  INVENTIONS. 


The  following  principle  of  the  science  of  invention  holds 
true  in  reference  to  a  large  class  of  past  scientific  inventions,  and 
it  may,  therefore,  be  assumed  to  hold  true  for  many  future  scien- 
tific inventions.  It  is  formulated  thus  : — 

An  invention  may  be  made  by  applying  one  or  combining  two 
or  more  principles  of  physical,  electrical,  or  chemical  sciences 
to  a  new  and  useful  purpose.  The  corollary  to  this  is  :  Any 
given  problem  of  invention  may  be  solved  by  becoming 
acquainted  with  the  principles  of  physics,  electricity,  and  chem- 
istry, and  then  searching  for  principles  which  by  their  combina- 
tion will  produce  the  result  sought. 

Both  of  these  principles  prove  the  preference  and  almost  the 
necessity  of  thorough  scientific  education  on  the  part  of  the  in- 
ventor. I  believe  it  would  be  for  the  good  of  the  industrial  arts 
and  the  public  to  establish  in  our  various  scientific  colleges 
a  class  for  the  development  of  the  power  of  inventing.  At  pres- 
ent, students  study  science  and  store  it  away  in  their  brains,  as 
though  the  storage  were  to  be  permanent.  By  the  time  they 
undertake  to  use  the  knowledge  they  have  forgotten  most  of  it. 

An  exercise  is  needed  whereby  the  student  will  be  encouraged 
and  assisted  in  making  use  of  the  scientific  principles  he 
learns.  Let  the  professor  of  this  department  give  the  student  a 
principle  for  application  to  some  useful  purpose.  If  the  in- 
vention proves  to  be  old  the  exercise  is  no  less  valuable.  It 
will  be  original,  even  if  not  novel,  and  will  thus  serve  to  train 
the  inventive  faculty  and  assist  in  forever  fixing  the  principle  in 
the  mind. 

Suppose,  for  instance,  that  he  should  be  asked  to  make  prac- 
tical use  of  the  electrical  principle,  that  the  substance  selenium 
is  a  conductor  of  electricity  when  exposed  to  light  and  a  non- 
conductor when  in  the  dark. 

We  can  imagine  one  student  proposing  to  solve  the  problem 
of  rising  with  the  sun.  He  would  have  an  electric  bell  in  cir- 


28 

cuit  with  an  electric  battery  and  with  a  piece  of  selenium, 
which  would  hang  in  the  window.  No  current  would  pass  in 
the  night  because  the  selenium  is  in  the  dark,  but  it  would  pass 
and  ring  the  bell  when  exposed  to  the  light  of  the  rising  sun. 
Another  student  would  probably  suggest  the  wonderful  in- 
vention of  the  photophone,  in  which  is  employed  this  principle 
for  transmitting  sound.  Another  student  might  propose  to  make 
a  meter  for  measuring  the  amount  of  energy  consumed  by  an  in- 
candescent lamp  during  each  month,  by  causing  the  selenium  to 
be  near  the  lamp.  While  the  lamp  was  in,  a  local  and  small 
current  would  flow  and  operate  the  clock-work;  when  the  lamp 
was  out,  the  clock-work  would  stop.  My  readers  may  per- 
haps think  of  as  many  different  applications  of  the  principle 
as  there  are  individuals,  and  some  may  result  in  a  val- 
uable and  novel  invention;  but  let  me  ask  how  many  such  ap- 
plications of  principles  and  facts  can  be  made  by  a  would-be 
inventor  if  he  does  not  know  the  principles  ?  Where  can  he 
find  these  principles?  In  books  and  periodicals  on  science;  in 
miscellaneous  readings  and  in  the  course  of  experiments.  He  can 
obtain  them  also  by  conversation  with  his  acquaintances, 
and  especially  from  those  who  have  made  a  systematic  study  of 
science. 

In  order  to  make  use  of  the  principle  of  invention,  set  forth 
in  the  last  corollary,  the  inventor  should  first  decide  what 
problem  he  wishes  to  solve  and  then  search  books  ;  search 
his  mind  for  any  hidden  principle  he  may  have  learned  a  long 
time  since;  converse  with  scientists  if  possible,  and  do  every- 
thing which  will  acquaint  him  with  the  principles,  and  as  each 
one  appears  think  upon  all  of  its  bearings,  to  discover  if  it  is 
possible  to  combine  it  with  another  principle  in  the  solution  of 
the  problem.  Suppose  the  problem  is  to  transmit  speech  elec- 
trically— /.  e.,  the  same  problem  that  was  solved  by  the  first  in- 
ventor of  the  telephone.  We  can  imagine  him  seeking  here 
and  there  for  the  principles  and  facts  in  the  science  of  sound, 
electricity,  and  motion.  He  considers  the  same  individually 
and  collectively. 

Or  suppose  we  consider  a  problem  which  has  not  yet  been 
commercially  solved,  the  conversion  of  an  alternating  current 
into  mechanical  power;  or,  more  briefly  stated,  the  invention  of 
a  commercial  alternating  current  motor,  printing  telegraph, 
electric  meter,  &c.  In  the  same  manner  that  other  great  in- 
ventions have  been  made  and  in  accordance  with  the  above 
stated  corollary,  the  inventor  must  review  the  simple  and  com- 
plex principles  and  facts  of  science  and  mechanics  with  the  ob- 
ject of  applying  the  same  to  the  solution  of  the  problem,  if  the 


29 

problem  is  capable  of  solution ;  that  inventor  who  does  this 
work  most  thoroughly  and  quickly  will  be  the  most  successful. 

One  of  the  greatest  difficulties  in  making  this  class  of  in- 
vention is  that  of  finding  or  recalling  the  principles  of  science. 
In  any  given  book  they  are  often  hidden,  or  it  may  be  necessary 
to  read  several  pages  in  order  to  obtain  a  single  principle  or 
fact.  Truths  of  science  are  the  most  valuable  tools  one  can 
possess  for  making  scientific  inventions.  The  inventor  cares 
not  how  or  when  or  by  whom  they  were  discovered.  He  cares 
for  nothing  except  to  know  them  and  then  to  use  them. 

Note  the  two  methods  of  procedure  as  set  forth  in  the  above 
principle  and  its  corollary  respectively  at  the  beginning  of 
this  chapter.  The  principles  are  given  in  the  following  chap- 
ters. Scientific  principles  have  another  value  to  the  inventor. 
They  furnish  him  with  that  knowledge  which  will  assist  in 
making  an  invention,  although  the  invention  may  not  consist 
primarily  of  the  combination  of  the  principles  used.  They 
may  sometimes  enter  in  merely  as  elements  of  construction,  not 
of  invention. 

Because  a  certain  principle  or  principles  have  been  applied 
to  produce  a  given  invention,  is  no  reason  that  they  cannot  be 
applied  in  a  subsequent  invention.  Take,  for  instance,  the 
principle  that  light  blackens  certain  compounds.  This  formed 
the  basis  of  the  invention  of  photographs.  Only  recently  it 
has  been  employed  by  W.  C.  Patterson  (the  invention  being 
owned  by  the  Walker  Electric  Meter  Co.).  He  allows  a  ray  of 
light  to  pass  through  an  eye  in  a  galvanometer  needle  and 
strike  a  moving  paper  covered  with  a  sensitive  photographic 
film.  In  this  way  he  photographs  the  movements  of  the 
needle.  The  area  within  the  curve,  by  calculation,  gives 
the  amount  of  energy  for  a  given  time  consumed  by  lamps, 
motors,  etc. 

In  this  book  it  would  be  useless  to  state  absolutely  every 
principle  and  fact  of  every  department  of  science.  Those  of 
probable  importance  to  the  inventor  are  given.  Those  which 
have  been  applied  once  or  twice,  etc.,  are  those  which  are  most 
apt  to  be  applied  again,  and  certain  old  principles  are  known 
which  have  never  been  applied  to  any  useful  purpose.  Out  of 
all  known  electrical,  physical,  and  chemical  knowledge,  those 
of  maximum  importance  to  the  inventor  have  been  formulated. 
An  inventor  can  make  scientific  inventions  without  neces- 
sarily making  discoveries.  The  scientific  principles  combined 
can  be  old.  How  fortunate  this  is  !  The  investigator  studies 
the  laws  of  nature  and  often  spends  a  lifetime  in  adding  only  one 
or  two  new  scientific  facts  or  principles  which  may  be  appropri- 


ated  by  the  inventor.  This  rule  of  invention  is  not  generally 
recognized.  The  popular  idea  is  that  an  invention  is  something 
radically  new — new  in  every  sense.  Argument  in  the  matter  is  use- 
less, provided  the  rule  can  be  established  by  the  proper  analysis 
of  important  inventions.  Several  examples  are  given  in  order  to 
prove  that  the  rule  is  applicable  in  nearly  every  case.  It  is  very 
seldom  that  the  inventor  both  discovers  and  invents.  He  makes 
use  of  the  scientific  knowledge  obtained  by  others.  He  uses  as 
his  tools  old  principles  and  facts — those  which  are  open  to  all. 

The  following  analyses  should  be  studied  very  carefully,  and 
the  inventor  should  analyze  in  a  similar  manner  other  inven- 
tions. The  exercise  is  of  great  benefit  as  a  preparation  for 
solving  problems.  If  he  clearly  comprehends  any  given  prob- 
lem solved  by  others  and  clearly  understands  that  it  has  been 
solved  by  the  combination  of  old  scientific  principles  or  facts, 
and  follows  the  combination  step  by  step  in  order  to  discern 
the  order  in  which  they  are  combined,  he  will  be  better  pre- 
pared to  undertake  new  problems,  and  will  not  be  so  apt  to 
travel  in  the  indefinite  footpath  laid  out  by  the  popular  mind, 
which  seems  to  think  that  the  invention  is  something  new  in 
absolutely  every  sense  ;  mysterious,  due  to  inspiration,  genius,  or 
to  some  peculiar  spirit  which  communicates  the  ideas  without 
any  preparation  for,  or  attempts  in,  solving  a  given  problem.  In 
the  analysis  each  problem  is  indicated  by  the  name  of  the  in- 
vention ;  and  the  principles  which  were  chosen  and  combined 
by  the  inventors  are  stated  as  briefly  as  possible.  It  is  easy  to 
assume  and  can  often  be  proved  that  the  inventor  in  each  case 
combined  many  principles  by  twos  and  threes,  etc.,  before  he 
obtained  the  right  combination,  and  that  he  obtained  the  desired 
results  with  other  combinations,  but  that  the  commercial  type 
was  the  best  of  them  all.  In  short,  let  the  inventor  notice  the 
probable  truths  : 

a.  That  the  principles  or  facts  combined  were  known  in 
nearly  every  instance  at  the  time  the  invention  was  made. 

b.  That  the  device  was  easy  to  design  and  construct  after 
the  right  combination  was  found. 

c.  That  the  principles  and  facts  are  usually  found  not  in  one 
department  of  knowledge,  but  that  a  chemical  fact  is  often  com- 
bined with  an  electrical  piece  of  knowledge,  a  heat  principle 
with  one  or  more  acoustic,  an  acoustic  with  electrical,  &c. 

d.  That  it  follows  that  if   past  inventions  have  been  thus 
made,  it  is  reasonable  to  believe  that  future  inventions  may  be 
made  in  the  same  manner. 

e.  That  the  inventions  would  not  have  been  made   if  the 
principles  and  facts  had  not  been  known. 


31 

/.  And  that  in  order  to  solve  any  given  problem,  the  in- 
ventor need  not  expect  to  succeed  until  he  has  investigated 
scientific  facts  and  principles  with  a  view  of  obtaining  the  ele- 
mental and  general  results  of  a  problem. 

Or  he  may  combine  principles  hap-hazard  to  learn  if  a  use- 
ful result  follows.  This  last  method  of  procedure  is  the  less  to 
be  recommended,  because  it  is  like  a  child  writing  promis- 
cuously the  characters  of  musical  notes,  flats,  sharps,  &c.,  upon 
five  parallel  lines  with  the  hope  that  a  new  tune  will  be  com- 
pcsed.  The  way  recommended  is,  first,  to  have  some  problem 
to  solve.  Ii  there  is  no  problem,  what  is  the  use  of  trying  to 
invent  ?  It  must  be  assumed  of  course  by  the  author  that  the 
inventor  has  problems  needing  solution.  Herein  is  a  good 
place  to  distinguish  the  musician  and  poet  from  the  inventor.  I 
have  seen  them  put  on  the  same  footing.  They  do  not  combine 
scientific  facts  and  principles.  They  combine  notes  and  words 
into  bars  and  verses  with  no  other  object  than  to  appeal  to  one 
or  more  of  the  senses  or  imagination.  Instead  of  saying  things 
in  the  ordinary  way,  the  poet  dresses  up  the  words  and  sen- 
tences to  appeal  more  forcibly  to  the  longing  one  has  of  listening 
to  the  beauties  of  the  particular  language.  A  translated  poem 
loses  its  charms,  but  an  invention  is  useful  independently  of  the 
nationality  of  the  user.  We  hear  of  the  musician  and  poet  as 
being  inspired,  as  having  genius,  and  as  being  exceptional,  and 
as  succeeding  not  in  proportion  to  anything  except  as  to  the 
amount  of  genius.  It  is  held  not  to  be  similar  with  the  inventor. 
He  has  a  definite  result  he  wishes  to  obtain;  he  must  undergo 
the  tedious  and  long  work  of  seeking  for  and  combining 
motions,  principles  and  facts  until  he  gets  that  combination 
which  will  solve  the  problem.  With  practice,  this  operation 
becomes  very  rapid.  The  reason  of  touching  upon  this  compari- 
son is  to  try  to  overcome  an  old  popular  notion  that  an  inventor, 
like  the  poet,  must  wait  for  the  inspiration.  He  who  believes 
in  waiting  is  more  likely  to  become  a  poet  than  an  inventor. 
The  analyses  alluded  to  above  are  as  follows  : 
Incandescent  Lamp  or  Subdivision  of  the  Electric  Current  for 
Lighting. — An  electric  current  is  converted  into  light  by  its  pas- 
sage through  a  conductor.  The  smaller  the  diameter,  and  the 
higher  the  specific  resistance  of  the  conductor,  the  greater  the 
completeness  of  the  conversion.  Carbon  has  the  Jiighest  specific 
resistance  of  all  practical  conductors,  and  is  incombustible  in 
a  vacuum.  Woody  fibres,  cotton  and  linen  thread  are  car- 
bonizable  at  a  high  heat,  whereby  pure  carbon  remains  having 
the  same  cellular  structure  as  the  original  material.  High  re- 
sistances in  parallel  subdivide  a  current,  so  that  a  small  portion 


goes  through  each.  Glass  and  platinum  have  the  same  rate, 
approximately,  of  expansion  by  heat,  explaining  why  for  so 
many  years  platinum  has  been  used  for  making  an  electric  con- 
nection from  the  exterior  to  the  interior  of  a  closed  glass  globe. 

Screw  Propeller  for  Ships. — The  rotary  motion  of  a  screw  in 
a  medium  produces  longitudinal  motion,  as  illustrated  by  the 
well-known  cider  press.  Experiment  showed  that  this  medium 
could  be  water.  This  illustrates  the  case  of  the  mere  applica- 
tion of  a  single  principle. 

Thermometer. — Heat  expands  liquids  proportionally  to  the 
temperature. 

Thermostat. — A  rod  made  of  two  strips  of  different  kinds  of 
metal  riveted  together  bends  through  an  angle  proportional  to 
the  temperature. 

Teslas  New  Phosphorescent  Light. — The  higher  the  potential 
of  an  electric  current  and  the  greater  the  frequency  of  alterna- 
tions of  current,  the  greater  the  light  during  discharge. 

Telegraph  Relay. — A  very  weak  current  may  be  concentrated 
by  passing  the  same  through  a  very  long  coil  of  wire  wound 
upon  a  core  of  iron.  Mechanical  motion  may  be  produced  upon 
a  delicately  movable  armature  within  inductive  relation  to  said 
core.  A  powerful  current  may  be  caused  to  flow  by  the  mere 
closing  of  a  circuit  needing  only  a  very  small  force. 

Electrical  Welding. — Heat  is  produced  at  loose  contacts  of 
metal  in  an  electric  circuit.  The  maximum  heating  power  of 
an  electric  current  is  in  a  secondary  coil  of  an  induction  coil. 
The  coarser  the  coil  in  proportion  to  the  fine  primary  coil,  the 
greater  the  heating  effects,  assuming  of  course  that  the  primary 
current  is  as  great  as  practicable. 

Air  Brake. — Friction  may  be  produced  and  a  wheel  prevented 
from  rotating  by  means  of  a  shoe  pressed  thereon  by  a  spring. 
Air  pressure,  if  sufficiently  great,  will  overcome  the  force  of  the 
spring,  reducing  the  friction  to  zero.  Pressure  of  air  may  be 
diminished  by  allowing  it  to  escape  from  its  compressed  con- 
dition into  the  open  atmosphere.  When  air  pressure  is  removed 
from  a  spring,  the  latter  assumes  its  original  pressure  and 
produces  friction  upon  the  wheel. 

Kinetograph. — The  phenakistoscope,  invented  years  and  years 
ago,  during  operation,  shows  to  the  eye  in  rapid  succession 
figures  of  an  animal,  a  man,  &c.,  in  different  relative  attitudes, 
producing  upon  the  eye  the  effect  of  one  figure  having  motion, 
in  view  of  the  persistence  of  vision.  In  this  instrument,  the 
figures  are  not  made  by  photography,  which  in  the  case  of  the 
kinetograph  are  true  to  life  if  made  at  a  high  rate  during  the 
motion  of  any  given  object. 


33 

Telephone. — Speaking  vibrates  the  air  and  membranes  in 
unison  with  the  larynx  in  the  throat.  A  vibrating  membrane 
always  produces  the  same  sound  for  the  same  vibrations.  A 
vibrating  iron  membrane  (armature)  vibrates  an  electric  current. 
A  vibratory  current  vibrates  an  iron  membrane  in  unison  with 
the  vibrations  of  the  current. 

Siphon  Recorder  for  Receiving  Cable  Dispatches. — A  liquid 
charged  with  static  electricity  and  located  in  an  open  capillary 
tube  is  expelled  therefrom,  overcoming  the  capillary  attraction 
between  the  tube  and  the  liquid.  A  paper  surface  moved  past 
the  stream  of  liquid,  which  may  be  ink,  receives  a  line,  whereas 
an  ordinary  pencil  or  pen  would  produce  friction,  which  would 
take  up  more  force  to  move  the  pencil  than  exists  in  the  current 
which  has  traversed  the  sea. 

Chlorine  Bleaching. — Chlorine  has  such  a  strong  attraction 
for  hydrogen  as  to  take  it  from  other  elements,  forming  a  gas 
which  escapes  into  the  air,  the  action  being  increased  by  the 
light  of  the  sun.  The  coloring  matter  in  fabrics  is  due  to  the 
presence  of  hydrogen,  which,  if  removed,  leaves  the  fabrics  white. 

Direct  Current  Dynamo. — A  closed  conductor  moved  to  and 
from  a  given  current  receives  an  induced  alternating  current. 
An  alternating  current  is  resolvable  into  a  direct  current  by  a 
pole  changer  acting  in  unison  with  the  alternations.  A  direct 
current  will  energize  a  magnet. 

Davy's  Safety  or  Mining  Lamp. — The  temperature  of  a  flame 
is,  for  any  given  oil,  a  certain  degree.  A  metal  introduced  into 
the  flame  reduces  the  temperature  immediately  about  the  metal, 
where  the  flame  becomes  extinguished  and  unburnt  carbon 
deposited,  so  that  a  fine  wire  gauze  prevents  a  flame  from  pass- 
ing through  the  same  and  appearing  on  the  opposite  side. 

Gas  Lighting. — Coal  heated  to  redness  out  of  contact  with 
air  generates  carbonic  mon-oxide  C  O,  and  carbureted  hydro- 
gen C  H4.  These  gases  are  combustible  in  air. 

Water  Gas  Lighting. — Water  vapor  in  contact  with  red  hot 
material  is  decomposed  into  hydrogen  and  oxygen,  which  are 
combustible,  relatively. 

Forbe's  Coulomb  Meter. — A  current  heats  a  wire.  A  heated 
wire  causes  a  rising  flow  of  air.  A  mill  is  operated  by  moving 
air.  Registering  apparatus  is  operative  by  a  windmill. 


34 
CHAPTER  X. 

ACOUSTIC  PRINCIPLES  AS  TOOLS  FOR  MAKING  SCIENTIFIC 
INVENTIONS. 


SPEAKING,  singing,  musical  instruments  and  other  sound 
producers  vibrate  the  air,  water  or  other  medium. 

That  against  which  the  vibrations  strike  vibrates  synchron- 
ously with  the  particular  medium,  and  in  unison  also  with  the 
membrane  in  the  throat  or  with  the  vibrating  element  of  the 
sound  producer. 

"  Sound  "  (/.  e.,  air  or  other  fluid  vibrations)  bounces  away 
from  a  surface  in  the  manner  of  a  ball  thrown  against  a  house, 
except  that  the  former  moves  in  a  straight  line. 

Sound  does  not  pass  through  substances  in  the  manner  of  a 
bullet  through  glass,  but  the  vibrations  given  to  the  glass  set 
the  air  on  the  other  side  into  vibration,  thereby  equivalently 
passing  through  the  glass  or  other  substance  considered. 

Sound  radiates  in  all  directions  from  the  sound  producer. 

Sound  may  be  concentrated  upon  a  point  by  producing  the 
sound  at  the  larger  end  of  a  funnel  or  directly  in  front  of  a 
concave  surface. 

When  the  smaller  end  of  the  funnel  or  a  convex  surface  is 
employed  the  sound  is  scattered. 

Sound  is  louder  the  nearer  the  sound  producer.  If  the  latter 
is  moved  double  the  distance  away,  the  sound  is  only  one- 
quarter  as  loud.  If  the  amplitude  of  vibrations  is  increased,  the 
sound  is  proportionally  increased.  The  denser  the  air,  liquid  or 
solid,  the  louder  the  sound.  In  the  direction  of  the  wind  the 
sound  is  louder  than  in  the  opposite  direction.  The  presence 
of  a  violin  box  or  similar  resonant  body  increases  the  sound. 
Sound  is  loud  according  to  the  degree  of  elasticity  of  the 
medium. 

A  tube  filled  with  air  or  water  conducts  sound  so  well  that 
a  sound  can  be  multiplied  several  times.  The  larger  the  tube, 
the  greater  the  length  may  be.  If  the  tube  is  twice  the  diam- 
eter, the  sound  may  be  conducted  twice  the  distance. 

Any  given  vibration  of  sound,  whether  vocal  or  instrumental, 
or  from  another  source,  has  a  velocity  of  1,100  feet  per  second, 
at  the  ordinary  temperature,  and  at  the  ordinary  atmospheric 
pressure.  In  water  the  velocity  is  5,000  feet  per  second. 

Metal  conducts  sound  with  a  velocity  of  1 6,000  feet  per  second. 

A  vibration  of  air  consists  of  a  condensation  and  a  rare- 
faction. The  air  is  first  compressed  and  under  abnormal  pressure, 


35 

and  then  it  expands  in  the  same  manner  as  a  solid  rubber  ball. 

Sounds  vary  in  pitch,  /.  .?.,  either  high  or  low.  The  greater 
the  number  of  vibrations,  the  higher  the  pitch,  like  a  pendulum. 
The  shorter  the  pendulum,  the  more  rapid  the  vibrations. 

Loud  or  soft  sounds  have  respectively  greater  and  less 
amplitude,  corresponding  respectively  to  a  pendulum  of  a  fixed 
length,  having  a  greater  or  less  swing.  This  property  is  called 
intensity. 

Sounds  also  have  quality,  which  varies  according  to  the 
material  which  produces  the  sound.  The  sounds  from  violins, 
pianos,  flutes  and  vocal  organs  come  from  different  materials, 
and  although  of  the  same  pitch,  and  intensity  are  of  different 
quality. 

Sound  added  to  sound  increases,  and  sound  opposing  sound 
diminishes  it. 

Air,  while  vibrated  by  sound,  is  as  truly  a  form  of  mechanical 
power  as  a  steam  engine. 

Sound  may  be  recorded  visually,  by  placing  the  sound  pro- 
ducer in  front  of  a  diaphragm  provided  with  a  point  resting 
upon  a  moving  surface  of  wax,  tin-foil  or  other  yielding 
substance. 

Sound  cannot  be  bottled  as  water,  but  the  records  obtained 
as  above  will  serve  as  a  guide  to  the  said  point,  so  that  by  a 
repetition  of  movement  of  the  surface  the  point  will  follow  the 
record  and  cause  the  diaphragm  to  vibrate  exactly  as  it  did 
before,  thereby  causing  the  air  to  vibrate  in  unison  and  produce 
the  sensation  of  the  same  sound  upon  the  ear  that  was  "stored" 
upon  the  surface. 

Sound  may  be  classified  as  musical,  articulate  (speech),  and 
miscellaneous.  Articulate  sounds  differ  from  the  others  in  the 
same  manner  that  a  continuous  but  irregular  current  differs  from 
intermittent  currents. 

An  ivory  ball  dropped  upon  a  stone  bounces  upward.  A 
portion  of  the  mechanical  energy  is  converted  into  heat ;  so  also, 
in  the  case  of  sound,  the  condensations  of  air  in  vibrating  pro- 
duce heat,  and  the  rarefactions,  cold.  The  condensations  and 
rarefactions  are  the  result  of  the  sound,  and  are  but  another 
name  for  vibrations. 

The  microphone  does  not  magnify  sound  in  the  same  sense 
that  a  microscope  magnifies  visible  objects.  The  action  is  that 
a  slight  sound  causes  the  carbon  contacts  to  intermittently  make 
and  break  a  large  electric  current,  which  operates  a  telephone 
receiver,  in  the  same  manner  that  a  relay  opens  and  closes  a 
local  circuit,  which  furnishes  the  energy  to  transmit  the  message 
to  double  the  distance  first  traveled  by  the  message. 


36 

Neither  does  the  microscope  magnify  light.  It  decreases  it; 
because  the  magnified  image  is  less  bright  than  the  object 
magnified. 

The  ticking  of  a  watch  at  the  end  of  a  long  metal  or  wooden 
rod  is  distinctly  audible,  while  through  air  at  the  same  distance 
the  sound  is  scarcely  heard.  Likewise  the  earth  conducts  sound 
better  than  the  air.  If  the  ear  is  applied  to  the  rails  of  a  rail- 
road, an  approaching  train  is  heard  long  before  it  can  be  heard 
in  the  air. 

All  kinds  of  sound  at  a  short  range  apparently  travel  with 
equal  rate,  because  the  music  from  a  brass  band  is  not  confused; 
but  those  of  greater  intensity  move  most  rapidly.  In  battles, 
those  at  a  distance  can  hear  the  report  of  a  cannon  before  the 
command  to  fire. 

The  velocity  of  sound  is  the  same  whether  traveling  horizon- 
tally or  vertically  through  the  air;  but  it  moves  faster  and  faster 
from  the  source  until  a  certain  maximum  is  obtained. 

A  bell  heard  through  a  tube  3,000  feet  long  is  heard  twice  at 
an  interval  of  over  two  seconds.  The  air  conducts  one  sound 
and  the  metal  of  the  tube  the  other. 

Wires  are  good  conductors  of  sound.  The  scratching  of  a 
telegraph  wire  can  be  heard  several  miles,  especially  if  the  wire 
terminates  in  a  membrane  which  terminates  at  the  ear.  Talking 
may  be  transmitted  through  a  wire  by  stretching  it  from  one 
membrane  to  another,  and  using  them  respectively  as  the  mouth 
and  ear  piece. 

Since  sound  is  reflected,  it  is  badly  conducted  by  a  substance 
formed  in  layers  or  separated  masses.  Poor  conductors  are  sub- 
stances like  plaster,  sand,  porous  earthenware,  ashes  and  shavings. 

Echoes  are  sometimes  heard  by  speaking  against  houses 
from  a  distance  of  100  feet  or  more  ;  but  they  may  be  produced 
at  any  time  by  means  of  a  concave  reflector  whose  radius  termi- 
nates in  the  speaker  at  anything  over  100  feet.  At  this  distance 
a  one-syllable  word  is  heard  reflected.  At  500  feet  five  syllables 
can  be  heard  by  reflection. 

Sound  is  reflected  by  clouds,  also  by  the  invisible  aqueous 
vapor  in  the  air. 

Lenses  made  of  membranes  between  which  is  a  liquid  or 
gas  concentrate  or  scatter  sound  as  truly  as  ordinary  lenses 
refract  the  rays  of  heat  and  light. 

The  air  may  vibrate  at  any  imaginable  rate,  but  the  ear  can- 
not distinguish  sound  if  the  number  exceeds  20,000  to  23,000 
per  second,  or  is  less  than  16  to  8  according  to  the  person  ;  for 
it  is  true  that  some  persons  can  hear  a  high  rate  of  23,000 
vibrations  per  second,  while  another  hears  it  not. 


37 

The  louder  the  sounds,  the  higher  the  note  which  is  audible. 
With  weak  sounds  the  ear  cannot  hear  a  note  having  over  about 
10,000  vibrations  per  second. 

If  several  clocks  are  placed  upon  a  shelf,  their  pendulums 
will  soon  vibrate  in  unison,  although  previously  they  were 
vibrating  differently. 

A  tuning  fork,  scarcely  audible,  if  placed  upon  a  board,  or 
a  piano,  is  audible  several  feet  away.  The  piano  having  a  large 
surface,  sets  a  large  mass  of  air  into  vibration,  and  therefore  the 
increased  loudness. 

If  a  tuning  fork  is  operated  in  front  of  a  small  hole  in  a  hol- 
low body  (resonator),  the  air  inside  will  or  will  not  loudly 
resound  according  to  the  volume  of  the  enclosed  air.  If  1,000 
tuning  forks  of  different  pitch  are  employed,  the  resonator  will 
answer  to  only  one  fork. 

The  mouth  is  a  resonator  for  the  sounds  produced  by  the 
larynx,  and  answers  to  all  notes  sung,  because  the  shape  and 
size  are  made  to  change  by  the  different  positions  given  to  the 
lips,  cheeks,  teeth,  tongue  and  jaws. 

The  longer  the  string  in  a  piano,  the  lower  the  note.  Men's 
voices  are  of  lower  pitch  than  those  of  women,  because  the 
vocal  strings  are  longer  in  the  former. 

Sound  produced  by  a  tuning  fork  is  simple — there  is  only 
one  rate  of  vibration.  That  produced  by  strings  is  compound, 
and  consist  first,  of  one  set,  giving  the  note  proper  ;  secondly, 
the  harmonics,  which  arise  from  vibrations  of  a  different  rate. 
The  following  analogies  will  explain:  A  rock  dropped  into  quiet 
water  is  like  a  tuning  fork,  producing  one  large  set  of  waves, 
but  no  small  one.  Immediately  after  the  rock  is  thrown,  cast  in 
some  smaller  stones  of  different  sizes.  Little  waves  are  visible 
upon  the  large  waves,  illustrating  to  the  eye  how  vibrations  of 
different  rate  and  amplitude  can  coexist. 

If  vibrations  of  two  sounds  having  vibrations  of  equal  length 
are  in  the  same  phase,  the  sound  is  doubled  ;  but  if  one  vibra- 
tion is  half  way  behind  the  other,  no  sound  is  heard.  If  the 
vibrations  are  of  different  lengths,  the  sounds  tremble,  /.  e.,  are 
alternately  loud  and  soft. 

A  gas  flame  sings  when  located  within  a  tube  open  at  both 
ends.  Some  of  the  air  is  consumed,  making  a  rarefaction  ;  then 
more  air  rushes  in,  causing  a  condensation,  and  so  on  in  such 
rapid  succession  as  to  produce  a  note.  The  gas  for  the  flame 
should  issue  from  a  finely  drawn  tube  projecting  upward  from 
a  gas  pipe.  This  tube  should  extend  into  the  first-named  tube. 

A  plate  fastened  at  its  centre  may  be  vibrated  by  a  violin 
bow  drawn  across  its  edge.  If  sand  is  placed  upon  the  plate  it 


210994 


forms  into  fanciful  figures,  according  to  the  point  of  application 
of  the  bow.  The  plate  may  be  fixed  at  the  edge  and  the  bow 
drawn  against  the  edge  of  a  central  hole.  A  membrane  stretched 
and  held  by  its  edges  and  vibrated  by  blowing  a  whistle  or  by 
other  sounds  arranges  sand,  placed  thereon,  in  regular  figures. 

Sounding  bodies  sometimes  attract  and  sometimes  repel  other 
bodies.  The  sounding  body  is  conveniently  a  violin.  A  balloon 
of  carbonic  acid  gas  is  attracted  toward  the  opening  in  the  box; 
one  of  hydrogen  is  repelled. 

Suspended  and  neighboring  tuning  forks  attract  each  other. 
A  piece  of  paper  suspended  by  a  silk  thread  and  near  a  sound 
producer  is  attracted  thereto  ;  or  a  card  may  be  fixed  and  a 
sounding  tuning  fork  suspended  near  it.  A  flame  is  repelled  by 
an  adjoining  sounding  body. 

Small  resonotors,  made  for  instance  of  small  pasteboard 
boxes,  containing  each  a  small  hole  and  mounted  upon  cross- 
arms  pivoted  at  the  centre,  revolve  about  the  pivot  when  a 
sounding  box  is  located  sufficiently  near. 

The  graphophone  differs  from  the  phonograph  in  that  in  the 
latter  the  record  on  the  wax  occurs  as  indentations,  while  in  the 
former  curves  are  marked  parallel  with  the  surface  of  wax. 


CHAPTER  XI. 

PRINCIPLES  IN    HEAT    AND  LIGHT    AS   TOOLS   FOR   MAKING 
SCIENTIFIC   INVENTIONS. 


HEAT  and  light  vibrate  the  molecules  of  a  body  ; — sound 
vibrates  the  body  as  a  mass. 

Heat  has  the  power  of  converting  solids  into  liquids;  liquids 
into  gases;  changing  the  color  of  metals,  as  by  making  them 
red  hot,  producing  electric  currents;  effecting  chemical  re- 
actions; producing  sound;  overcoming  magnetism;  and  develop- 
ing mechanical  motion. 

Light  may  be  converted  into  heat,  electricity,  magnetism; 
and  it  will  produce  chemical  decomposition  and  mechanical 
power. 

Heat  and  light  act  in  opposition  to  that  of  cohesion,  as 
illustrated  by  its  converting  a  solid  into  a  gas;  the  volume  of 
the  gas  being  greater  than  that  of  the  solid. 

Heat,  in  vibrating  the  molecules  of  an  animal's  body  pro- 
duces a  sensation  which  is  also  called  heat;  but  science  uses 


39 

this  term  to  indicate  the  vibration  of  the  molecules  of  a  body 
or  of  that  of  the  medium  between  bodies,  said  medium  having 
the  property  of  communicating  heat  from  one  body  to  another. 

When  two  bodies  of  different  temperatures  are  brought 
together,  the  motions  of  the  molecules  of  the  one  are  communi- 
cated to  those  of  the  other,  which  becomes  warmer;  finally  the 
molecular  motions  of  both  are  communicated  to  surrounding 
objects,  until  reduced  to  the  normal  condition. 

In  a  manner  somewhat  similar  to  sound  being  communicated 
from  one  body  to  a  distant  one  by  vibration  of  intermediate 
air,  so  heat  and  light  are  assumed  to  be  communicated  by  an 
atmosphere  so  thin  and  light  that  it  cannot  be  detected  by  any 
present  known  means. 

Heat  and  light  are  not  intercepted  by  a  vacuum;  but  sound 
is  cut  off. 

Solids,  liquids  and  gases  differ  from  one  another  because  of 
the  relative  positions  and  motions  of  the  molecules. 

In  gases,  the  heat  has  entirely  overcome  the  force  of  cohe- 
sion; so  that  the  distance  between  the  molecules  depends  only 
upon  the  pressure  of  an  external  medium  and  upon  gravitation. 
At  a  thousand  miles  above  the  earth  the  molecules  of  the  air 
are  probably  many  feet  apart. 

In  solids,  the  molecules  vibrate  within  fixed  limits;  and 
when  moved  beyond  those  limits  by  mechanical  force  the  body 
is  divided  into  separate  masses. 

In  liquids,  the  forces  of  heat  and  cohesion  are  nearly  bal- 
anced, and  remain  so  between  fixed  temperatures  under  any 
given  atmospheric  pressure. 

In  solids,  the  distance  between  the  molecules  is  less  than  in 
liquids,  and  less  yet  than  in  gases. 

A  vapor  is  an  intermediate  state  between  a  liquid  and 
gas.  The  forces  of  cohesion  and  heat  are  more  nearly  balanced  in 
a  vapor  than  in  any  other  form.  A  slight  reduction  of  temperature 
or  increase  of  pressure  causes  liquefaction.  A  slight  elevation 
of  temperature  or  decrease  of  pressure  causes  gas. 

Some  solids  have  the  property  of  vapors,  in  that  they  are 
convertible  directly  into  a  gas  by  heat  without  first  becoming  a 
liquid. 

The  molecules  of  an  enclosed  gas  strike  upon  and  rebound 
from  the  inner  surface  of  the  containing  vessel;  the  resultant  of 
all  the  forces  being  pressure  which  is  increased  by  heat.  If  the 
gas  is  enclosed  in  a  yielding  vessel,  as  of  rubber,  the  volume  of 
the  vessel  increases  by  heating. 

The  volume  of  a  solid  or  liquid  likewise  increases  by  heating 
and  diminishes  by  cooling. 


40 

What  is  true  of  light  is  true  of  heat,  because  light  is  usually 
heat;  but  what  is  true  of  heat  is  not  necessarily  true  of  light, 
because  heat  exists  without  light. 

The  sum  of  the  forces  exerted  upon  a  surface  by  the  mole- 
clues  of  a  gas  results  in  a  constant  resultant  pressure. 

In  order  to  show  the  rapidity  of  vibrations  of  molecules,  it 
has  been  proved  that  the  number  of  impacts,  in  a  second,  of  a 
molecule  of  gas  upon  a  surface  is  4,700  millions.  The  length  of 
the  path  of  the  molecule  at  ordinary  temperature  and  pressure 
is  in  length  equal  to  .000000095  of  a  yard.  The  diameter  of  a 
molecule  of  hydrogen  is  approximately  .0000000008  yard. 

Heat  produces  three  effects  upon  a  body.  i.  It  increases 
the  volume.  In  doing  this,  it  overcomes  the  pressure  of  the 
atmosphere  or  other  surrounding  fluid.  2.  It  increases  the  rate 
of  vibration,  which  is  the  cause  of  rise  of  temperature. 
Work  is  expended  to  do  this  in  a  manner  similar  to  work  being 
expended  in  increasing  the  number  of  vibrations  per  minute  of 
a  cannon  ball  or  of  the  piston  of  a  steam  engine.  3.  It  in- 
creases the  swing  or  amplitude  of  the  vibration.  Work  is  there- 
fore expended,  as  in  the  case  of  a  piston;  the  further  it  is  moved, 
the  more  the  energy  expended. 

Of  solids,  liquids  and  gases,  the  same  are  expansible  by  heat; 
gases,  most;  solids,  least;  and  liquids,  at  a  medium  rate. 

The  expansion  may  be  mostly  in  one  direction,  as  with  a  rod; 
in  two  directions,  as  in  a  sheet;  or  in  three  directions,  as  in  a 
cubical  block. 

The  temperature  of  a  body  corresponds  to  the  pressure  of  a 
liquid  or  to  the  electromotive  force  of  an  electric  current.  A 
thimbleful  of  water  may  have  the  same  temperature  as  a 
barrelful. 

The  expansion  of  solids,  liquids  or  gases  is  proportional  to 
the  temperature;  /.  e.  to  the  rate  of  vibration  of  the'molecules. 

A  globule  of  mercury  or  other  liquid  in  a  fine  tube  is  moved 
considerably  by  heating  the  air  in  a  bulb  formed  on  the  end  of 
the  tube.  The  air  expands  and  drives  the  globule  along  the 
tube. 

A  fine  evacuated  capillary  glass  tube  is  acted  upon  gradually 
by  the  pressure,  so  that  after  a  year  or  two  the  diameter  of  the 
tube  is  less. 

Different  kinds  of  substances  have  different  degrees  of  ex- 
pansion under  the  same  amount  of  heat. 

In  a  similar  manner  that  a  short  magnet  is  more  quickly 
magnetized  and  demagnetized  by  an  electric  current  than  a  long 
magnet;  so  does  a  thermometer  mercury  column  change  more 
rapidly  in  length  the  smaller  the  bulb  thereof. 


41 

Increase  of  density  in  any  given  substance  increases  the 
rate  of  expansion  per  unit  of  heat. 

Among  familiar  substances,  the  following  solids  are  more 
and  more  expansible  by  heat  in  the  order  named:  Diamond, 
wood,  graphite,  compound  minerals,  glass,  platinum,  steel,  iron, 
copper,  lead,  ice,  gutta-percha. 

The  sources  of  cold  and  their  degrees  are: — mixed  bisulphide 
of  carbon  and  nitrous  acid — 140°  C.;  ether  mixed  with  the  vapor 
of  carbonic  acid  when  liberated  from  the  confined  liquefied  car- 
bonic acid — no°;  Arctic  regions — 58°;  liquefying  of  mercury 
from  the  solid  state — 40°;  mixture  of  snow  and  salt — 20° 

Red  heat  of  metals  is  obtained  at  550°.  Fusion  of  silver, 
1,000°;  of  cast  iron,  1,530°;  of  platinum,  2,000°:  blast  furnance, 
i, 800°. 

The  heating  of  one  side  of  a  long  rod  causes  that  side  to 
expand,  while  the  other  side  remains  cool  for  a  while;  conse- 
quently the  rod  bends.     If  the  rod  is  made  of  different  metals  ' 
the  rod  will  bend  when  heated,  because  one  metal  expands  more 
than  the  other  for  any  given  amount  of  heat. 

Heat  may  be  made  to  break  thick  glass  by  heating  one  side 
and  cooling  the  other. 

Through  the  expansion  of  bodies  heat  becomes  a  form  of 
mechanical  energy. 

Heat  varies  a  current  in  expanding  a  rod  pressing  upon  car- 
bons touching  one  another  while  forming  a  part  of  an  electric 
circuit.  The  more  the  rod  is  heated,  the  closer  the  carbons 
come  in  contact,  and  consequently  the  greater  the  current. 

Non-crystalline  substances  expand  by  heat,  equally  in  all 
directions.  With  certain  crystals  the  expansion  is  not  the  same 
in  all  directions. 

A  substance  besides  that  of  type  metal,  which  contracts 
upon  heating  and  expands  on  cooling,  is  argentic  iodide. 

Independently  of  the  kind  of  gas,  whether  air,  hydrogen, 
chlorine,  coal  gas,  or  any  other  gas,  the  amount  of  expansion 
for  the  same  amount  of  heat  is  approximately  the  same. 

Metals  become  just  visibly  red  at  525°  C.;  dull  red,  at  700°; 
cherry  color,  at  900°;  orange,  at  1,100;  white,  at  1,300°;  brilliant 
white,  at  1,500°. 

A  gas  will  pass  through  platinum  at  as  high  temperature  as 
through  porous  earthenware,  but  not  to  such  a  degree. 

When  a  solid  is  heated  sufficiently  to  approximately  over- 
come the  force  of  cohesion,  it  becomes  viscous  or  liquid,  accord- 
ing to  the  nature  of  the  substance. 

The  temperature  for  fusion  is  different  with  different  sub- 
stances. The  following  are  some  illustrations:  Ice  fuses  at 


42 

o°  C;  phosphorus,  at  44°;  wax,  at  65°;  fusible  metal,  at  68°; 
sodium,  at  90°;  sulphur,  at  114°;  lead,  at  335°;  aluminium,  at 
850°;  and  platinum,  at  1,775°. 

Heat  applied  to  solids  increases  the  temperature,  but  as 
soon  as  fusion  begins  the  temperature  remains  constant  until 
the  whole  solid  has  been  converted  into  a  liquid. 

The  same  principle  is  true  in  regard  to  the  conversion  of  a 
liquid  into  a  gas. 

Glass  and  iron  are  examples  of  those  solids  which  pass 
through  all  the  stages  of  viscosity  before  becoming  a  true  and 
thin  liquid.  Of  such  substances  the  melting  temperatures  are 
all  the  temperatures  between  those  at  which  viscosity  begins 
and  ends. 

The  melting  point  may  be  raised  by  increasing  the  atmos- 
pheric pressure  upon  the  substance  heated. 

Generally,  an  alloy  of  metals  fuses  at  a  lower  temperature 
than  any  of  the  metals  composing  it. 

A  mixture  of  a  metal  and  non-metal  usually  fuses  at  a  lower 
temperature  than  the  metal.  Steel  (containing  infusible  carbon) 
melts  at  very  much  lower  temperature  than  iron. 

The  principle  is  true  generally  for  non-metals.  Sodic  and 
potassic  chlorides,  when  mixed,  fuse  at  a  lower  temperature  than 
either  when  alone. 

Heat  may  be  stored  by  converting  a  solid  into  liquid  or 
liquid  into  gas;  when  the  gas  becomes  a  liquid  again  or  the 
liquid  a  solid,  the  same  amount  of  heat  is  given  out. 

Equal  quantities  of  ice  and  hot  water  intimately  mixed  are 
found  to  assume  a  temperature  of  o°  before  the  ice  is  all  melted. 
This  water  at  zero  mixed  with  an  equal  quantity  of  water  at  a 
higher  temperature  results  in  water  at  an  average  of  the  two 
temperatures. 

Most  solids  may  become  liquefied  not  only  by  fusion,  but  by 
solution.  Common  salt  for  instance  fuses  at  a  comparatively 
high  temperature,  but  at  any  temperature  above  o°  it  may  become 
a  liquid  by  solution  in  water.  Some  substances,  practically  in- 
fusible, are  convertible  into  a  liquid  by  solution.  Solids  which 
are  opaque  often  become  transparent  by  solution. 

A  liquid  is  limited  in  its  capacity  of  dissolving  solids.  After 
a  certain  amount  has  been  dissolved,  any  additional  amount 
remains  undissolved,  unless  the  temperature  is  increased.  The 
temperature  of  a  liquid  is  decreased  during  the  process  of 
dissolving  therein  a  solid, 

If  the  solid  and  liquid  enter  into  chemical  combination,  the 
temperature  increases,  decreases,  or  remains  constant,  according 
to  the  nature  of  the  substances.  With  cold  quick-lime  and 


43 

water  (whereby  the  new  substance,  calcic  hydrate,  is  formed)  the 
mixture  becomes  very  hot.  The  two  substances  combine  to 
form  a  new  compound.  Where  no  chemical  combination 
occurs  the  temperature  lowers.  Where  the  heat  produced  by 
chemical  action  is  equal  to  the  cold  produced  by  conversion  of 
a  solid  into  a  liquid,  the  temperature  remains  the  same. 

Heat  is  the  force  which  determines  crystallization,  which  may 
be  obtained  by  solidifying  bodies  by  slowly  evaporating  the 
liquid  from  their  solution  or  by  slowly  solidifying  from  a  state 
of  fusion. 

Water  containing  no  air  in  solution  freezes  at  15°  lower 
temperature  than  water  in  which  air  is  absorbed.  The  water 
should  be  kept  very  quiet.  Air  may  be  removed  from  water  by 
long  boiling. 

Violent  agitation  of  a  liquid  at  a  freezing  point  prevents 
solidification. 

When  strong  salt  water  freezes,  the  ice  is  practically  pure. 
Of  solids  and  liquids  of  the  same  substance,  the  latter  are 
greater   in   volume.     Certain  substances  heretofore  named  are 
exceptions. 

Water  expanding  on  solidification  is  thought  to  be  due  to 
the  fact  that  the  crystals  occupy  more  space  than  if  it 
solidified  without  crystallization.  When  the  crystals  melt, 
the  mobile  liquid  fills  up  the  space  formerly  left  between 
the  crystals. 

Certain  substances,  as  gelatine  and  gum  arabic,  do  not  lower 
the  temperature  of  water  while  dissolving. 

Sodic  iodide,  at  a  slight  additional  pressure  of  atmosphere, 
boils  while  melting. 

Any  liquid  at  any  temperature  boils  in  a  vacuum.  To  main- 
tain the  boiling,  the  vacuum  must  be  maintained. 

The  vapors  of  liquids  relatively  insoluble  produce  double 
the  pressure  of  either;  those  more  or  less  soluble  in  each  other 
exert  less  than  double  the  pressure  of  either.  Place  water  and 
benzole  in  an  enclosed  space.  The  pressure  is  double  that 
which  either  the  water  vapor  or  benzole  vapor  would  give 
alone. 

Connect  two  vessels  containing  respectively  ice  water  and 
hot  water.  The  pressure  of  the  vapor  in  each  is  the  same  as  that 
which  would  exist  in  the  cooler  vessel  if  the  other  were  absent. 
This  principle  holds  true  with  all  vapors. 

The  rate  of  evaporation  varies  with  the  temperature,  the 
amount  of  vapor  of  the  same  liquid  in  the  atmosphere,  the  sur- 
face of  liquid  exposed,  and  the  changes  in  the  nature  of  the 
surrounding  atmosphere. 


44 

The  following  are  the  boiling  points  of  some  important 
liquids: — water,  100°  C.;  mercury,  358°;  melted  zinc,  940°; 
benzole,  80°;  alcohol,  39°;  liquefied  nitrous  oxide,  92°. 

The  boiling  point  is  higher  in  case  the  liquid  contains  solid 
substances  in  solution.  Concentrated  salt  water  boils  at  202°  C. 
The  boiling  point  is  lowered  if  the  liquid  contains  gaseous  or 
volatile  substances  in  solution. 

Water  covered  with  a  film  of  sweet  oil  boils  at  a  higher  tem- 
perature than  when  not  so  covered.  A  slight  explosion  occurs 
when  the  temperature  reaches  120°  C.,  and  then  the  liquid  boils. 

Water  boils  in  glass  vessels  at  106°  C.,  and  in  metal  vessels 
at  100°.  A  piece  of  metal  placed  in  the  glass  vessel  makes  the 
water  boil  at  100°. 

Water  boils  at  lower  and  lower  temperatures,  the  further 
upward  it  is  moved  from  the  earth. 

Water  cannot  be  boiled  in  an  enclosed  vessel  except  at  a 
very  high  temperature  when  it  turns  immediately  into  steam. 
Remove  air  from  water  by  ordinary  boiling.  Place  a  little  of 
the  water  in  a  thick  sealed  glass  tube.  Heat  to  200°  C.  The 
water  instantly  disappears.  The  experiment  is  of  course 
dangerous,  as  the  pressure  is  500  lk>.  per  sq.  in. 

In  an  enclosed  space  containing  air  a  vapor  will  enter,  in  the 
same  manner  that  sugar  will  enter  water.  In  other  words  a  gas 
will  dissolve  a  vapor.  The  pressure  within  the  vessel  will  be  in- 
creased the  same  as  if  the  vapor  were  entering  a  vacuum. 

A  liquid  assumes  a  globular  form  when  dropped  upon  a  hot 
surface  (above  the  boiling  point).  The  globule  rests  upon  a 
cushion  of  the  vapor  of  the  liquid.  As  soon  as  the  temperature 
of  the  plate  falls  to  that  which  allows  the  globule  to  be  in  actual 
contact  with  the  plate,  the  globule  bursts  violently  into  steam. 
The  temperature  of  the  globule  is  below  the  boiling  point.  Upon 
the  same  principle,  men  have  been  able  without  injury,  to 
plunge  their  wet  hands  into  melted  lead. 

WATER  in  a  porous  vessel  grows  colder.  The  evaporation  at 
the  surface  produces  the  cold. 

A  liquid  may  be  separated  from  another  liquid,  as  ether 
from  alcohol,  by  heating  to  the  boiling  point  of  the  more  volatile 
liquid  (ether)  which  passes  into  a  receiver,  while  the  alcohol  re- 
mains behind.  Similarly,  a  gas  may  often  be  liberated  from  a 
solid,  even  if  chemically  combined  therewith.  Coal  gas  may 
thus  be  separated  from  coal. 

By  high  pressure  and  low  temperature,  a  gas,  even  air,  car- 
bonic acid,  and  ammonia,  may  be  converted  into  a  liquid. 
Oxygen  in  liquid  form  is  colorless  and  transparent,  and  in 
evaporating  has  a  temperature  of — 181°  C. 


45 

Partially  fill  a  metallic  vessel  with  water.  Add  ice  and  a 
thermometer.  The  temperature  falls.  -At  a  certain  temperature 
dew  will  immediately  form  upon  the  vessel. 

Some  good  absorbents  of  moisture  from  the  air  are  phosphoric 
anhydride;  quick-lime;  strong  sulphuric  acid;  calcic  chloride 
and  cobaltic  chloride.  Paper  saturated  with  the  latter,  dried, 
and  then  put  into  damp  air  turns  from  blue  to  pink,  and  when 
taken  to  dry  air  becomes  blue.  Heat  will  also  turn  it  blue. 

If  a  thermometer  bulb  is  wet  with  water,  alcohol,  ether,  &c., 
the  temperature  falls  in  proportion  to  the  dryness  of  the  air. 

Hair  has  the  property  of  lengthening  considerably  by  absorp- 
tion of  moisture.  Twisted  catgut  strings  untwist  when  moist 
and  twist  while  drying.  Similar  actions  occur  with  paper 
coated  on  opposite  sides  respectively  with  gelatine  and  varnish. 

Radiated  heat  can  be  transmitted  through  a  medium  with- 
out appreciably  increasing  the  temperature. 

Light  is  not  conducted  by  a  substance,  but  heat  is.  If  lumi- 
nous paint  is  exposed  in  parts  to  light,  the  parts  not  exposed 
give  no  light  in  the  dark.  If  light  were  conducted  in  the  man- 
ner of  heat,  the  paint  would  appear  equally  luminous  in  the 
dark.  Many  substances,  as  glass,  will  allow  light  to  pass  through 
the  same,  but  the  light  is  not  conducted  in  the  same  sense  as 
heat. 

As  with  electricity,  so  with  heat,  substances  have  different 
conductivities.  The  best  conductors  of  heat  are  usually  the 
best  conductors  of  electricity. 

Different  substances  conduct  heat  at  widely  different  veloc- 
ities; and  electricity  is  conducted  by  different  substances  at 
approximately  the  same  velocity.  There  is  a  difference  in  the 
electrical  velocities,  but  it  is  scarcely  detectible  for  ordinary 
distances. 

Heat  is  conducted  in  wood  better  in  the  direction  of  the 
fibre  than  transversely. 

The  mixed  double  mercuric  and  cupric  iodide  under  the 
influence  of  heat  turns  from  bright-red  color  to  dark  purple. 

Copper  is  100  times  a  better  heat  conductor  than  water. 

Water  becomes  heated  principally  by  circulation.  One  part 
becomes  heated.  It  rises  like  a  cork  and  the  cold  water  takes 
its  place,  and  so  on  until  the  whole  mass  is  heated.  For  this 
reason  the  heat  should  be  applied  at  the  bottom.  Alcohol  may 
be  burned  on  the  top  of  water,  and  yet  just  below  the  surface 
the  water  is  cold;  showing  that  water  is  a  very  poor  conductor 
of  heat.  Gases  conduct  heat  even  less  than  water,  but  they 
will  allow  heat  and  light  to  pass  through.  Liquids  become  hot 
by  the  process  of  circulation,  as  in  the  case  of  water. 


Heat  is  communicated  from  one  body  to  another  with  a  rate 
dependent  upon  the  number  of  points  in  contact.  The  maxi- 
mum amount  is  conducted  in  any  given  time  by  having  very 
smooth  surfaces  of  contact. 

Rays  of  heat  and  light  are  projected  from  a  body  equally  in 
all  directions,  and  lie  in  straight  lines. 

Rays  of  light  and  heat  may  be  bent  by  allowing  them  to  pass 
obliquely  from  any  given  medium,  as  air,  into  a  denser  medium, 
as  glass,  or  a  rarer  medium,  as  rarefied  air. 

From  any  given  mass  heat  and  light  are  radiated  in  direct 
proportion  to  the  amount  of  radiating  surface;  and  according 
to  the  color.  They  are  radiated  best  from  a  rough  black  sur- 
face, as  made  with  lamp-black. 

Both  heat  and  light,  like  sound,  are  reflected  from  a  sub- 
stance. Not  all  is  reflected  ;  a  portion  is  absorbed  by  the 
substance. 

The  angle  at  which  the  heat  and  light  are  reflected  is  equal 
to  that  at  which  they  fall  upon  the  surface.  Echoes  are  re- 
flected sound.  The  surface  reflecting  the  sound  seems  to  origi- 
nate the  sound;  similarly,  a  white  house  seems  to  be  the  source 
of  light;  whereas  the  light  coming  from  it  is  reflected  light. 

The  rays  of  reflected  light  and  heat  are  in  the  same  plane  as 
those  which  fall  upon  the  surface. 

Reflected  heat  and  light  may  be  reflected  repeatedly  and  in- 
definitely, but  a  fraction  disappears  each  time  by  absorption. 

A  bright  concave  surface  brings  the  rays  of  light  and  heat 
to  a  focus;  a  convex  surface  scatters  them. 

In  the  highest  attainable  vacuum  heat  and  light  are  reflected 
as  well  as  in  the  open  air;  and  in  compressed  air  as  well  as  in 
air  at  the  ordinary  atmospheric  pressure. 

The  cold  rays  from  ice  or  similar  substance,  when  focused, 
reduce  the  temperature  of  that  which  is  placed  in  the  focus. 

A  flame  radiates  little  heat  in  proportion  to  its  high  tem- 
perature; but  an  incombustible  mass,  as  platinum,  placed  in  the 
flame  causes  a  large  increase  of  radiated  heat. 

A  ray  of  heat  or  light  is  a  series  of  vibrations.  In  a  ray  of 
sound  the  vibrations  travel  about  1,100  ft.  in  a  second;  in  the 
case  of  heat  and  light,  the  speed  is  such  that  only  about  eight 
seconds  elapse  in  the  transit  of  a  vibration  from  the  sun  to  the 
earth — 93,000,000  miles. 

Sound  vibrates  the  mass;  light  and  heat  vibrate  the  mole- 
cubs  of  the  mass. 

In  the  same  sense  in  which  the  ear  does  not  distinguish 
sound  if  the  vibrations  are  above  or  below  a  certain  rate,  so  the 
eye  does  not  distinguish  light  below  or  above  a  certain  rate  of 


47 

vibration.  There  are  3,000  nerves  from  the  ear  to  the  brain,  all 
tuned  to  as  many  different  sounds.  The  shortest  respond  to  the 
highest  notes;  the  lowest  to  the  lowest  notes;  so  also,  in  the  case 
o-  the  eye,  there  is  a  power  of  seeing  only  when  the  number  of 
vibrations  is  within  certain  limits. 

An  electric  crurent  at  the  instant  of  rupture  or  closing,  in 
circuit  with  one's  head,  causes  the  nerves  of  the  eye  to  vibrate 
in  unison  with  the  vibrations  of  the  current,  so  that  in  the  dark 
a  slight  flash  of  light  is  produced,  but  no  object  becomes  visible. 
Three  Leclanche  cells  of  ordinary  size  will  not  injure  the  eyes. 
The  flash  appears  as  if  one  were  winking. 

Let  a  body  be  heated  from  o°  C.  to  an  indefinitely  high  tem- 
perature. The  emitted  heat  vibrations  are  added  to  by  more 
rapid  vibrations  as  the  temperature  rises.  The  first  vibrations 
visible  occur  at  such  a  rate  as  to  produce  the  sensation  of  red. 
Violet  rays  are  due  to  the  most  rapid  of  those  which  produce 
sensation  of  light.  Chemical  effects  are  produced  by  rays 
which  have  a  higher  rate  than  those  which  produce  violet  and 
by  violet  rays  also. 

If  a  ray  of  light  (which  is  accompanied  by  heat)  falls  upon  a 
three-sided  piece  of  transparent  substance  (called  a  prism)  and 
strikes  a  surface  in  an  otherwise  dark  room,  the  vibrations  of 
the  ray  are  separated  from  one  another,  occupying  a  long  rec- 
tangular area,  when  projected  upon  a  surface. 

Violet  is  seen  at  one  end  and  red  at  the  other.  Just  beyond 
the  violet,  where  no  light  is  visible,  exist  chemical  rays,  because 
they  will  turn  photographic  paper  black  and  produce  other 
chemical  actions.  Just  beyond  the  red,  where  no  light  is  visible, 
a  thermometer  indicates  heat.  Throughout  the  limit  between 
red  and  violet  are  heat,  light  and  chemical  rays.  The  strongest 
heat  rays  are  at  the  red;  the  strongest  chemical  rays  at  the 
violet;  and  the  strongest  light  rays  at  the  yellow.  The  combi- 
nation of  all  the  color  rays  forms  the  original  white  sun- 
light. 

The  seven  colors  may  be  combined  by  reflecting  each 
by  a  mirror,  so  as  to  strike  all  at  the  same  spot.  The  spot 
appears  white.  Lenses  may  also  be  employed  to  combine 
the  rays. 

The  seven  colors,  violet,  indigo,  blue,  green,  yellow,  orange, 
red,  are  simple  and  cannot  be  analyzed;  but  two  or  more  can  be 
compounded  to  form  other  colors. 

The  above  principles  teach  what  is  otherwise  found  to  be  a 
fact,  that  an  incandescent  body,  as  the  sun,  radiates  simul- 
taneously vibrations  of  different  rates,  and  that  they  do  not 
interefere  with  one  another 


48 

A  bright  object  is  visible  after  it  has  been  placed  behind  an 
opaque  screen.  This  is  due  to  the  fact,  that  an  image  formed  in 
the  eye  remains  after  the  object  is  removed.  Let  a  disc  be 
painted  with  the  colors  of  the  rainbow  arranged  as  the  pieces  of 
a  pie  when  cut.  If  the  disc  is  rotated  rapidly  it  appears  white. 
The  colors  mix  in  the  eye.  Before  one  color  disappears  from 
any  given  spot  the  others  overlap. 

If  the  red  and  green  and  yellow  of  the  spectrum  are  reflected 
by  mirrors  upon  a  given  spot,  white  light  is  produced.  Com- 
pounded green,  yellow  and  violet  produce  white;  also  orange 
and  blue.  Colored  pigments  cannot  be  used,  as  they  are  absorb- 
ents of  colors.  Mixed  yellow  and  blue  paints  produce  green, 
and  so  on  with  greatly  different  results  from  those  obtained  by 
mixing  spectral  colors. 

Light  produced  by  combustion  is  seldom  simple.  The 
yellow  light  of  the  gas  flame  contains  blue,  red,  orange,  &c. 
Common  salt  burned  in  alcohol  gives  nearly  a  pure  yellow  light. 
Roses  have  no  color,  because  no  red  is  present  in  such  a  flame. 
A  man's  face  looks  deadly  pale  in  such  a  light. 

Pure  red  is  obtained  by  passing  daylight  through  glass 
colored  with  cuprous  oxide;  pure  blue  by  passing  through  a 
solution  of  cupric  sulphate,  and  pure  red  by  passing  daylight 
through  a  solution  of  ferric  sulpho-cyanide  of  iron. 

Rock  salt,  i  inch  thick,  transmits  92  percent,  of  heat;  smoking 
quartz,  67;  glass,  39;  alum,  12;  ice,  6;  and  cupric  sulphate,  none. 

Heat  is  largely  "lost  "  in  its  passage  through  glass;  but  that 
which  has  passed  through,  passes  through  a  second  piece  of 
glass  with  practically  no  loss.  When  alum  and  rock  salt  are 
superposed  they  are  opaque  to  light  and  heat. 

If  i  represents  the  amount  of  heat  absorbed  in  its  passage 
through  air,  i, 200  represents  the  amount  absorbed  by  ammonia  gas. 

If  a  gas  is  allowed  to  rush  into  a  vessel  both  become  heated, 
because  the  molecules  of  the  air  strike  against  the  side  of  the 
vessel,  whereby  the  force  of  motion  is  partially  converted  into 
the  force  of  heat. 

When  a  gas  is  rapidly  exhausted  from  a  vessel,  cold  is  pro- 
duced, because  the  heat  produced  in  the  manner  above  stated 
is  converted  into  motion. 

The  best  absorbents  of  heat  are  the  best  radiators. 

Elementary  gases,  as  hydrogen,  oxygen,  &c.,  are  worse 
.absorbents  of  heat  and  light  than  compound  gases,  like  carbonic 
acid,  coal  gas,  &c. 

White  substances  absorb  the  least  and  black  the  most  light 
;and  heat.  An  exception  is  that  of  plumbic  carbonate  (white 
.lead),  which  absorbs  heat  as  fast  as  lamp-black. 


Or) 


49 

Snow  covered  by  some  black  substance  melts  faster  than 
when  bare. 

Drops  of  water  often  cause  the  surface  under  the  same  to 
burn  when  both  are  exposed  to  sunlight.  The  drops  absorb 
the  heat  and  at  the  same  time  focus  it  upon  the  surface,  because 
the  drops  have  the  shape  of  a  lens. 

Rock  salt  covered  with  lamp-black,  or  with  iodine  stops  light, 
but  transmits  heat. 

A  hothouse  becomes  warm  because  the  light  reflected  from 
objects  within  is  reduced  to  polarized  and  heat  rays  to  which 
glass  is  opaque. 

Of  any  different  substances  absorbing  heat  one  will  increase 
in  temperature  faster  than  the  other.  They  both  are  exposed 
to  the  same  heat,  but  the  temperature  of  the  one  rises  faster  than 
that  of  the  other.  Mercury  rises  in  temperature  much  more 
rapidly  than  water.  The  former  is  said  to  have  a  higher  specific 
heat  than  the  latter. 

The  specific  heat  of  any  substance,  when  liquid,  is  higher  than 
when  solid.  Water  will  get  hot  about  twice  as  fast  as  ice. 

The  figure  denoting  the  specific  heat  indicates  how  many 
times  more  heat  is  required  to  raise  the  temperature  of  the  sub- 
stance through  i°  than  to  raise  the  temperature  of  water  i°. 
The  atomic  weight  indicates  how  much  heavier  an  element  is 
than  hydrogen.  The  product  of  the  specific  heat  and  atomic 
weight  of  any  elementary  substance  is  approximately  a  constant 
quantity,  and  equal  to  about  6. 

Rubbing  or  pressing  substances  together  produces  not  only 
static  electricity,  but  also  heat  and  sometimes  light. 

All  substances,  even  ice,  have  heat,  and  it  is  believed  that 
absolute  cold  has  never  been  obtained;  but  that  it  would  exist 
only  when  the  molecules  are  so  close  together  as  to  be  incapable 
of  motion. 

Other  sources  of  heat  are  the  sun,  electricity,  chemical 
changes,  those  bodies  which  are  warmer  than  the  thing  to  be 
heated,  percussion,  terrestrial  heat,  absorption  and  animal 
heat. 

Heat  produced  by  friction  is  greater,  the  greater  the  rela- 
tive motion  and  pressure. 

Pieces  of  ice  rubbed  together  in  a  vacuum  melt. 

Water  shaken  is  increased  in  temperature  about  i°. 

Flint  rubbed  against  steel  detaches  steel  particles  which  are 
so  hot  as  to  burn  with  scintillation. 

The  movement  of  shooting  stars  through  the  air  at  their  high 
velocity  causes  so  much  heat  that  they  burn  at^  a  white  heat, 
the  same  being  invisible  before  reaching  the  earth's  atmosphere. 


50 

A  tube  filled  with  water  and  rapidly  rotated  between  two 
sticks  may  be  made  to  boil. 

The  temperature  of  a  body  rises  in  a  certain  proportion  to 
the  increase  of  its  density.  Air  compressed  in  a  tube  by  a  piston 
becomes  heated. 

Shot  fired  against  an  iron  mass  produces  light  visible  at 
night;  showing  that  mechanical  motion  is  converted  into  heat 
and  light.  Iron  when  hammered  becomes  hot.  In  general, 
percussion,  as  well  as  friction  and  pressure,  produces  heat. 
Lead  is  not  increased  in  density  by,  but  becomes  hot  upon, 
hammering. 

The  amount  of  heat  received  by  the  earth  from  the  sun 
in  a  year  is  capable  of  melting  a  coating  of  ice  upon  the  surface 
of  the  earth  160  ft.  in  thickness;  which  is  .0000000005  part  of 
the  total  heat  of  the  sun. 

By  descending  into  the  earth  30  yards  (more  or  less  according 
to  the  location)  the  temperature  remains  constant  during  sum- 
mer and  winter.  The  heat  is  independent  of  the  sun  and  is  due 
to  a  source  of  heat  within  the  earth. 

Upon  approaching  toward  the  center  beyond  30  yards  the 
temperature  increases;  about  i°  for  every  90  feet.  At  a  depth  of 
30  miles  the  temperature  would  be  sufficient  to  melt  all  known 
substances.  The  amount  of  heat  received  at  the  earth's  surface 
from  the  internal  heat  is  .0001  that  received  from  the  sun. 

Substances  become  warm  while  absorbing  gases.  Platinum 
becomes  so  hot  by  absorbing  oxygen  gas  that  a  stream  of 
hydrogen  passed  over  the  same  ignites.  While  charcoal  absorbs 
gases  its  temperature  is  increased. 

If  chemical  actions  are  slow,  heat  is  scarcely  perceptible. 
The  same  chemical  actions,  when  rapid,  apparently  generate  a 
larger  amount  of  heat.  Wood,  while  decaying,  gives  off  the 
same  aggregate  heat  as  the  same  quantity  of  wood  burned  in  a 
fire. 

All  ordinary  combustion  is  obtained  from  the  union  of  the 
oxygen  of  the  air  with  the  substance  burned. 

Luminosity  does  not  depend  upon  temperature. 

Phosphorus  when  rubbed  emits  light.  An  alcohol  flame, 
almost  non-luminous,  is  of  much  greater  temperature  than  that 
of  a  candle  flame. 

Hydrogen  and  oxygen  when  burning  give  no  light,  but  give 
the  hottest  known  flame. 

Luminous  paint,  placed  in  sunlight  and  removed  to  a  dark 
room,  gives  light  for  hours,  but  its  temperature  is  not  abnormal. 
Diamonds  and  a  few  other  substances  have  this  property  of 
luminous  paint. 


51 

Fire-flies  give  much  light,  but  practically  no  heat. 

The  amount  of  heat  produced  by  hydrogen  burning  in 
oxgyen  is  17  times  greater  than  that  of  wood  in  oxygen;  while 
the  light  in  the  former  is  practically  zero.  In  the  Geissler  tube 
light  is  produced  without  heat,  but  the  luminosity  is  too  little 
for  commercial  use. 

Although  charcoal,  graphite  and  diamond  are  all  pure  car- 
bon, yet  the  combustion  of  each  gives  a  different  quantity  of 
heat;  but  the  quantity  is  the  same  in  the  aggregate  if  the 
densities  are  taken  into  account. 

In  an  animal  the  force  of  chemical  affinity  is  converted  into 
mechanical  motion.  The  oxygen  taken  in  at  the  lungs  and  the 
food  at  the  mouth  undergo  chemical  changes,  which  are  repro- 
duced in  the  forms  of  heat  and  motion. 

Oxygen  unites  with  carbon  to  form  carbonic  acid  in  animal 
life.  In  vegetable  growth  the  carbon  is  taken  from  the  carbon, 
liberating  the  oxygen.  The  oxygen  which  is  consumed  by 
animal  life  to  form  carbonic  acid  is  liberated  by  plants  which 
take  the  carbon  only. 

Oxidation  of  iron,  wood,  &c.,  produces  heat.  Oxidation  of 
the  muscles  produces  mostly  contraction  of  the  muscles,  but 
little  heat. 

Plants  store  heat  during  growth  and  give  it  out  during  decay 
or  combustion.  An  exception  is  at  the  time  of  blossoming. 
Oxidation  then  occurs  and  the  temperature  of  the  plant  rises,  as 
in  animals. 

The  temperature  of  a  flame  is  increased  by  increasing  the 
rapidity  of  the  supply  of  oxygen. 

Highly  compressed  air  allowed  to  exit  into  the  air  on  a 
summer's  day  produces  a  shower  of  snow-flakes. 

Compressed  air  escaping  upon  a  thermopile  in  circuit  with 
a  galvanometer  deflects  the  needle  in  one  direction,  while  air 
from  a  bellows  deflects  the  needle  in  the  opposite  direction. 

A  pin-hole  in  paper  or  other  thin  membrane  acts  as  a  lens  in 
a  camera.  An  image  of  an  object  in  the  light  formed  in  the 
dark  is  inverted. 

Light  vibrations  have  an  actual  velocity  about  185,000 
miles  per  second. 

The  brightness  of  a  surface  exposed  to  light  radiating  from 
a  luminous  point  is  quartered  when  the  distance  is  doubled. 
Heat,  light  and  sound  vary  inversely  as  the  square  of  the 
distance. 

If  a  surface  is  inclined  to  a  ray  of  light  the  brightness 
varies  with  the  cosine  of  the  angle.  Cosines  of  angles  are  found 
explained  in  books  on  trigonometry. 


52 

A  grease  spot  on  paper  practically  disappears  when  equally 
illuminated  from  opposite  sides,  but  grows  darker  and  darker, 
the  greater  the  difference  of  brightness  on  opposite  sides. 

The  intensity  of  sunlight  is  670,000  candle-power. 

Light  travels  in  a  straight  line,  but  may  be  bent  by  allowing 
it  to  pass  obliquely  to  or  from  a  denser  or  rarer  medium,  or  to 
be  reflected  at  an  angle  from  a  mirror. 

A  ray  of  light,  as  a  whole,  may  be  vibrated  by  rapidly  inter- 
rupting the  same  by  an  opaque  object,  by  vibrating  a  mirror;  by 
varying  the  medium  through  which  it  passes;  by  vibrating  a 
lens  or  prism  which  transmits  the  light;  or  by  a  combination  of 
two  or  more  of  the  above  means. 

A  ray  of  light  may  be  regulated  as  to  intensity  and  quantity 
by  any  of  the  means  named  for  vibrating  it. 

The  image  formed  by  one  lens  or  reflector  may  be  made 
larger  by  a  second  lens  or  reflector.  Light  is  magnified  by  con- 
centrating to  a  focus,  as  is  the  case  with  heat  and  sound. 

The  light  from  stars  is  bent  and  re-bent,  and  reflected  by 
entering  the  denser  atmosphere  about  the  earth,  and  conse- 
quently the  appearance  of  "  twinkling." 

A  substance  appears  red  because  it  absorbs  all  the  other 
colors  composing  white  light  and  reflects  only  red.  In  a 
similar  manner  substances  appear  blue,  green,  yellow,  &c. 

Red  glass  is  red  by  transmitted  light,  because  red  passes 
through  the  glass  while  other  colors  are  reflected  or  absorbed. 
So  with  glass  of  other  colors. 

Colorless  glass  is  that  which  transmits  all  the  colors. 

A  red  object,  as  a  rose,  has  no  color  in  a  room  where 
only  blue  light  exists,  and  so  also  with  a  green  object  in  light  of 
a  different  color.  Although  a  gas,  candle  or  oil  flame  has  a 
yellow  appearance,  yet  nearly  all  colors  exist.  The  yellow  is  in 
excess.  So  also,  some  bodies  appearing  of  a  certain  color  re- 
flect other  colors,  which  are  not  visible,  because  overshadowed 
by  the  prominent  color. 

Place  paper  of  one  color  upon  paper  of  a  different  color. 
Fix  the  eyes  upon  the  same,  and  jerk  the  top  paper  away.  The 
remaining  paper  has  a  color  different  from  either.  The  papers 
should  be  in  daylight  and  the  time  of  observation  about  one 
minute.  The  color  of  the  top  paper  remains  in  the  eye  after  re- 
moval and  mixes  with  the  color  from  the  bottom  paper,  form- 
ing a  color  composed  of  the  two  colors. 

The  spectrum  is  the  name  given  to  the  heat,  light  and 
chemical  rays  eminating  from  a  source  of  heat  and  light,  after 
analysis  by  a  prism.  The  heat  rays  are  slowest  in  vibration 
and  the  chemical  most  rapid,  while  light  rays  are  medium. 


53 

Anything  which  will  reduce  the  rate  of  vibration  of  chemical 
rays  will  convert  them  into  light  rays  ;  and  similarly  light  rays 
would  be  converted  into  heat  rays. 

The  sulphides  of  barium,  calcium  or  strontium,  commonly 
called  luminous  paint,  give  off  blue  light  when  placed  in  the 
chemical  rays,  which  are  otherwise  invisible.  The  rate  of  vibra- 
tion in  the  chemical  rays  is  reduced  to  that  of  bluish  light.  The 
color  varies  with  the  temperature  of  the  sulphide  and  whether 
the  sulphide  of  barium,  calcium  or  strontium  is  employed.  The 
last  named  at  20°  C.  is  violet;  at  40°,  blue;  at  70°,  yellow;  at 
100°  (boiling  point  of  water),  orange;  and  at  200°,  almost  in- 
visible. The  light  is  emitted  without  extra  heat.  It  may  be 
called  cold  light. 

The  maximum  time  of  luminosity  of  luminous  paint  is  30 
hours. 

For  a  few  seconds  or  fraction  of  a  second  the  following 
substances  possess  similar  properties  of  luminious  paint  : 
Diamonds,  amber,  milk  sugar,  cane  sugar,  dry  paper,  silk,  Ice- 
land spar,  uranium  compounds.  By  means  of  a  special  instru- 
ment called  a  phosphoroscope  the  last-named  substance  is 
caused  to  become  visible  in  a  dark  room  .04  second  after  ex- 
posure to  light.  It  has  a  higher  candle-power  than  luminous 
paint,  but  lasts  only  the  above  fraction  of  a  second.  Many  sub- 
stances are  not  phosphorescent.  For  example,  phosphorus, 
after  which  the  property  is  named.  Phosphorus  appears  light 
in  the  dark,  simply  because  it  unites  with  oxygen.  It  is  not 
light  in  a  vacuum,  nor  does  exposure  to  light  have  any  more 
effect  than  darkness.  Other  non-phosphorescent  substances 
are  liquids,  metals,  quartz  and  sulphur. 

By  heating  diamonds,  or  the  mineral  chlorophane,  to  300°  C. 
(red  heat  of  metals  being  525°),  the  same  become  luminous 
and  remain  so  for  several  days,  although  the  temperature  falls 
to  the  ordinary  degree  of  the  atmosphere. 

Light  stored  by  luminous  paint  is  increased  by  heating  ;  but 
the  luminosity  lasts  for  a  proportionally  less  time. 

In  the  same  manner  that  phosphorescent  substances  con- 
tinue to  vibrate  in  unison  with  light  rays,  so  do  many  bodies 
continue  to  radiate  heat  when  taken  from  a  source  of  heat,  and 
generally  the  molecules  of  all  bodies  are  in  continual  vibration 
or  else  absolute  cold  would  exist. 

When  a  source  of  heat,  light  or  sound  rapidly  approaches  a 
person,  the  vibrations  are  more  numerous  per  second  ;  and 
when  moving  away,  less  frequent.  Illustration:  An  approach- 
ing whistling  locomotive  has  the  sound  of  a  higher  and  higher 
pitch,  and  when  receding  the  note  descends  in  pitch. 


54 

Some  substances  have  the  property  of  appearing  of  different 
colors  according  to  the  angle  at  which  they  are  looked  at 
relatively  to  the  source  of  light.  They  are,  in  part,  tincture  of 
night-shade  or  curcuma,  extract  of  horse-chestnut,  thin  flakes  of 
fuchsine,  a  solution  of  sulphate  of  quinine,  aesculine,  and  canary 
glass  (colored  with  compounds  of  uranium),  a  solution  of  chlor-o- 
phyl  in  alcohol,  and  a  decoction  of  madder  in  alum.  The  effects 
are  best  seen  with  the  help  of  a  lens,  which  concentrates  the 
rays  upon  the  substance. 

Canary  glass  held  in  the  light  which  comes  into  a  dark  room 
through  blue  cobalt  glass  is  yellow  ;  because  the  high  rate  of 
vibration  in  blue  rays  is  reduced  by  the  yellow  glass  to  that 
number  of  vibrations  which  produces  yellow  light. 

Polished  silver  exposed  to  iodine  vapor  acquires  a  flim  of 
argentic  iodide,  which  will  turn  black  upon  exposure  to  light. 
The  black  substance  is  insoluble  in  sodic  hyposulphite,  while 
argentic  iodide  is  soluble.  Mercury  vapor  is  condensed  upon 
the  black  surface,  but  not  upon  argentic  iodide.  The 
black  substance  is  mostly  pure  silver  in  a  very  finely  divided 
state. 

A  photographic  glass  plate  is  glass  which  has  been  coated 
with  collodion  or  gelatine  containing  potassic  iodide  and 
washed  with  an  aqueous  solution  of  argentic  nitrate. 

"  Bromiodide  emulsion "  containing  an  aniline  dye  is  not 
only  the  most  sensitive  to  light,  but  is  also  highly  sensitive  to 
yellow  light,  so  that  yellow  objects  appear  white  in  a  positive 
photograph.  With  other  ordinary  photograph  preparations  the 
blackening  in  the  negative  is  caused  only  by  the  violet  and 
chemical  rays,  and  not  by  yellow. 

A  negative  in  the  development  of  which  ferrous  sulphate  is 
used  instead  of  sodic  hyposulphate,  a  bath  of  potassic  cyanide 
turns  to  a  positive. 

The  eye  of  an  animal  is  a  camera.  It  is  provided  with  a 
sensitive  surface,  which  receives  the  image  and  connects  with 
the  brain  by  thousands  of  nerves.  At  the  point  where  the 
nerves  join  the  eye  blindness  exists,  as  may  be  proved  by  hold- 
ing a  white  card,  having  two  small  black  spots,  at  reading  dis- 
tance, the  distance  between  the  spots  being  equal  to  that  between 
the  eyes.  Close  the  left  eye  and  keep  the  other  directed  upon 
the  left  spot.  The  right  spot  is  invisible  because  its  image  falls 
upon  the  spot  where  all  the  nerves  join.  The  eye  has  its  lens 
liquid  for  preventing  the  heat  from  injuring  the  eye;  means 
for  adjusting  the  focus  according  to  the  distance  of 
the  object  viewed;  and  a  variable  opening  for  regulating 
the  amount  of  light. 


55 

The  image  formed  within  the  eye  is  inverted,  as  in  a 
camera,  but  the  brain,  in  some  unknown  manner,  is  so  impressed 
that  objects  appear  in  their  true  position. 

A  cannon  ball  during  transit  past  the  eyes  is  invisible.  If 
itself  luminous,  a  streak  of  light  appears.  If  non-luminous, 
but  illuminated  by  a  flash,  the  ball  appears  as  though  it  were 
stationary.  Also,  the  spokes  of  a  rapidly  rotating  wheel  appear 
to  stand  still  during  a  flash  of  lightning  at  night,  whereas,  in 
daylight  the  spokes  are  not  separately  visible.  The  above  facts 
show  that  an  impression  remains  upon  the  eye  only  when  the 
eye  views  an  object  an  appreciable  length  of  time.  A  lighted 
candle  viewed  for  a  minute  appears  again  when  extinguished, 
and  then  disappears  and  reappears,  and  varies  in  color,  becom- 
ing orange,  then  red,  then  violet,  and  greenish  blue,  showing 
that  some  colors  remain  upon  the  retina  or  sensitive  surface  of 
the  eye  longer  than  others.  White  light  remains  longest,  then, 
in  order,  yellow,  red  and  blue. 

White  or  bright  objects  against  a  black  or  dark  background 
appear  larger,  and  black  against  white,  smaller  than  the  real 
size.  Illustration  :  A  church  steeple  at  a  distance  appears  to 
lean  over,  due  to  unequal  illumination  of  opposite  sides.  Ob- 
jects of  one  color,  surrounded  by  a  different  color,  are  accom- 
panied in  the  eye  by  a  fringe  or  edging  of  a  color  different 
from  either. 

In  the  same  sense  that  all  the  different  vibrations  due  to  an 
orchestra  reach  the  ear  without  confusion,  so  do  all  the  colors 
in  a  picture  produce  no  confusion  in  the  eye.  The  different 
colors  give  different  rates  of  vibration  to  different  nerves. 
Violet  light  corresponds  to  a  high  note  and  red  light  to  a  low 
pitch.  The  length  of  a  vibration  or  swing  of  an  atom  in  pro- 
ducing the  red  is  .000027  in.,  and  in  the  case  of  violet,  .000015  m- 

Lenses  of  gla^s  produce  single  images  in  a  camera.  Lenses 
of  certain  crystals,  as  Iceland  spar,  produce  double  images. 
Glass,  when  annealed  or  compressed,  has  this  property  of  double 
refraction.  Such  doubly  refracting  substances  cause  objects  to 
appear  double  when  looked  through.  Besides  Iceland  spar,  the 
following,  among  other,  substances  have  the  property  of  double 
refraction  :  Tourmaline,  sapphire,  ruby,  sodic  nitrate,  quartz  and 
ice. 

Two  rays  of  one  color — /.  e.,  having  one  set  of  vibration 
(white  light  having  as  many  sets  of  different  rapidity  of  vibration 
as  there  are  colors) — may  be  made  to  interfere  and  annihilate 
each  other  by  reflecting  them  from  slight  angular  surfaces  upon 
a  wall.  Alternate  black  and  white  lines  are  visible,  whereas 
the  black  lines  disappear  if  one  ray  is  removed.  If  white  light 


56 

is  used,  the  black  and  bright  lines  are  replaced  by  lines  of  differ- 
ent colors. 

Place  a  coin  in  a  vessel.  Look  into  the  vessel  over  its 
edge  so  that  the  coin  is  just  out  of  sight,  and  add  water. 
The  coin  comes  into  sight.  The  reflected  light  in  coming 
from  the  denser  fluid,  water,  is  bent  in  coming  to  the  rarer 
fluid,  air. 

Every  object  casts  two  shadows,  a  central  or  dark  and  a 
fringe  or  light  shadow. 

In  a  camera  an  image  exists,  even  if  there  is  no  surface  to 
receive  it. 

Pictures  of  a  man  running,  each  picture  showing  each  suc- 
ceeding position  of  the  limbs,  head,  feet,  &c.,  brought  rapidly 
before  the  eye  and  rapidly  removed  so  that  the  eye  sees  one 
figuie  at  a  time,  and  all  the  figures  in  rapid  succession,  make 
such  an  impression  upon  the  eye  as  to  form  a  single  living  pic- 
ture. The  instrument  for  doing  this  generally  is  called  a  phena- 
kistoscope.  When  the  different  positions  are  taken  by  photo- 
graphy, it  is  called  a  kinetograph.  They  illustrate  the  principle 
that  an  image  remains  upon  the  retina  of  the  eye  an  appreciable 
length  of  time. 

When  air  vibrates  to  produce  sound,  the  particles  move  to  and 
fro,  as  if  in  a  cylinder  in  front  of  a  reciprocating  piston.  The 
air  is  alternately  compressed  and  rarefied.  In  the  case  of  heat 
and  light,  a  medium  is  supposed  to  exist  in  which  the  heat  and 
light  travel  as  vibrations,  but  the  particles  have  motions  in 
straight  lines  perpendicular  to  the  direction  in  which  the  light 
is  moving.  They  have  the  same  motion  as  particles  in  a  wave 
of  water.  The  wave  travels  along  horizontally,  but  the  particles 
of  water  move  up  and  down.  The  waves  of  a  rope  illustrate  the 
vibrations  of  light  and  heat.  The  particles  of  a  rope  move 
transversely  thereto.  All  facts  uphold  the  above  statements  in 
regard  to  the  nature  of  heat,  but  it  is  still  theoretical.  As 
to  sound,  no  doubt  exists  as  to  its  consisting  of  condensa- 
tions and  rarefactions  of  a  mass,  whether  solid,  liquid,  or 
gaseous. 

Chemical  rays  of  light — /.  e.,  those  beyond  the  violet — may 
be  stored  by  almost  any  substance.  Illustration  :  Expose  an  en- 
graving or  drawing  or  any  print  to  sunlight.  Take  it  to  a  dark 
room  and  press  it  upon  photographic  paper.  The  engraving 
will  be  photographed.  The  chemical  rays  absorbed  by  the 
paper  produce  the  reactions  in  the  same  manner  as  the  sun, 
only  much  more  slowly.  In  printing  photographs,  the  process 
continues  in  a  dark  room  after  exposure  to  light.  After  a  few 
hours  the  effect  is  noticeable. 


57 
CHAPTER     XII. 

PRINCIPLES  IN  CHEMISTRY  AS  TOOLS  FOR  MAKING  SCIENTIFIC 
INVENTIONS. 


EVERY  compound  body,  as,  for  instance,  water,  is  composed 
of  elements,  the  smallest  particle  of  a  compound  being  a  mole- 
cule, and  the  smallest  part  of  an  element  an  atom.  This  prin- 
ciple is  the  foundation  of  chemistry.  Iron,  for  example,  is  com- 
posed of  atoms  of  the  same  kind;  therefore  iron  is  an  element. 
No  one  has  ever  been  able  to  find  that  it  is  a  compound.  No 
known  chemical  action  discovers  anything  but  iron.  The  small- 
est particle  which  exists  is  therefore  composed  of  iron  and  is 
called  an  atom.  Now  let  the  iron  be  caused  to  rust.  By  this 
means  the  iron  combines  with  the  atoms  of  another  element 
called  oxygen.  The  smallest  particle  of  the  compound  rust  or 
iron  oxide  is  a  molecule.  If  this  molecule  is  analyzed  it  is 
found  composed  of  iron  and  oxygen.  The  number  of  elements 
is  comparatively  few,  but  compounds  are  numbered  by  the  hun- 
dred. Some  compounds  are  natural,  but  most  have  been  made 
artificially,  and  there  is  no  reason  known  why  others  cannot  be 
made.  At  long  intervals  a  new  element  is  discovered,  but 
knowledge  of  chemistry  shows  that  if  others  are  found  they  will 
probably  be  rare  and  practically  useless. 

There  are  about  sixty-three  elements  which  may,  as  far  as 
known,  be  composed  of  other  elements.  The  composition  of 
compounds  may  be  known  by  analysis  through  the  agency  of 
burning  them  and  studying  the  flame  with  a  spectroscope,  each 
substance  giving  its  own  peculiar  visual  signal. 

The  solvent  power  of  water  is  greater  in  scope  and  magni- 
tude than  that  of  any  other  substance. 

Substances  which  are  merely  mixed  together  are  not  com- 
pounds, and  may  be  separated  therefrom  by  mechanical  filtra- 
tion, by  evaporation  or  distillation,  or  by  hand. 

Elements  of  a  compound  which  have  a  stronger  attraction 
for  other  elements  than  for  each  other  will  leave  the  former  and 
unite  with  the  latter,  as  illustrated  by  zinc  in  contact  with  sul- 
phuric acid — it  takes  the  oxygen  and  sulphur  from  the  sulphuric 
acid  and  liberates  the  hydrogen. 

Whenever  two  or  more  elements  combine  to  form  a  com- 
pound the  said  compound  differs  from  either  element  in  one  or 
all  of  the  following  respects  :  Conductivity  of  heat,  sound  and 
electricity,  hardness,  weight,  color,  and  more  or  less  in  other 
physical  properties. 


58 

The  composition  of  bodies  is  generally  made  known  by  re-  - 
acting  upon  them  with  other  known  compounds  or  elements. 
Thus,  common  salt  looks  like  a  thousand  other  substances  and 
tastes  like  other  compounds,  and  its  other  physical  properties 
are  much  like  those  of  other  compounds.  How  shall  its  com- 
position be  known  ?  React  upon  it  with  sulphuric  acid  and 
manganic  oxide  under  the  influence  of  heat.  A  green  gas  issues 
which  will  bleach  vegetable  colors.  This  gas,  chlorine,  could 
not  have  come  from  the  sulphuric  acid  nor  the  manganic  acid, 
therefore  it  must  have  come  from  the  common  salt ;  by  reactions 
of  other  chemicals  it  is  found  that  the  common  salt  contains 
sodium.  By  means  of  chemical  reactions  compounds  may  be 
made  as  well  as  analyzed.  If  sodium  is  introduced  into  the 
green  gas  and  heated,  a  bright  fire  is  caused,  resulting  in  a  white 
smoke,  which  is  found  to  be  common  salt,  chemically  called 
sodic  chloride. 

Compounds  may  also  be  analyzed  by  the  electric  current. 
If  the  terminals  of  a  circuit  are  placed  in  an  aqueous  solution 
of  cupric  sulphate  pure  copper  is  separated  from  the  sulphate 
and  deposited  upon  one  of  the  terminals.  Scarcely  a  compound 
exists  which  is  not  decomposed  by  the  passage  of  an  electric 
current  through  its  aqueous,  acid  or  alkaline  solution.  Com- 
pounds may  also  be  formed  by  the  electric  current.  Thus,  if  the 
current  in  the  above  is  closed  upon  itself  the  deposited  copper 
on  the  terminal  unites  with  one  or  more  of  the  elements  of  the 
electrolyte  and  forms  a  compound  therewith.  A  current  passed 
from  one  lead  terminal  to  another  of  the  same  substance  in  an 
electrolyte  of  sulphuric  acid  causes  the  compound  known  as 
plumbic  peroxide  to  be  formed  upon  one  of  the  lead  terminals. 
If  the  source  of  current  be  removed  and  the  terminals  closed 
upon  themselves,  the  plumbic  peroxide  becomes  analyzed  to 
such  an  extent  as  to  be  reduced  to  a  lower  oxide,  which  is  a 
new  compound,  differing  widely  in  chemical  and  physical  prop- 
erties from  the  peroxide. 

An  electric  current  will,  therefore,  sometimes  analyze  com- 
pounds and  sometimes  combine  elements  into  compounds.  This 
is  also  true  of  heat  and  light. 

Chemicals  often  combine  or  separate  by  reactions  upon  one 
another  at  the  ordinary  temperature. 

It  is  by  chemical  actions  that  life  is  supported.  Hold  a  glass 
tube  in  the  mouth  and  breathe  through  the  same  while  the  other 
end  dips  in  clear  lime-water.  Soon  the  water  becomes  milky, 
due  to  the  formation  of  carbonate  of  lime.  The  oxygen  which 
enters  the  lungs  combines  with  carbon  of  the  body,  forming  car- 
bonic acid  gas,  which  when  exhaled  unites  with  the  lime  and 


59 

forms  carbonate  of  lime.  In  a  perfectly  closed  room,  10  feet 
on  each  side,  death  would  ensue  in  a  very  few  hours  because  the 
oxygen  would  be  used  up.  The  life-giving  oxygen  would  be 
turned  into  the  poisonous  carbonic  acid. 

Vegetable  life  is  supported  by  chemical  action.  Grains  con- 
tain phosphorus  ;  therefore  fertilizers  for  grains  should  contain 
phosphates.  Ammonia  occurs  in  manures,  and  it  is  from  that  gas 
that  plants  obtain  their  nitrogen.  The  leaves  are  the  nostrils  of 
the  plants,  whereby  the  carbonic  acid  of  the  atmosphere  is  inhaled 
so  that  the  plants  may  possess  carbon,  which  may  subsequently 
be  obtained  by  means  of  a  kiln. 

Metals,  generally,  are  reduced  from  their  ores  by  chemical 
reactions.  The  ores  are  mixed  with  those  substances  with  which 
the  non-metallic  elements  of  the  ores  have  stronger  attraction 
than  the  metals.  Those  ores,  which  are  oxides,  may  be  mixed 
with  carbon  and  heated  to  a  high  temperature.  The  oxygen 
leaves  the  metal  and  joins  the  carbon,  forming  carbonic  acid, 
which  escapes  into  the  atmosphere,  leaving  the  metal  free.  Car- 
bonate ores  are  mixed  with  lime.  The  carbonic  acid  leaves  the 
metal  under  high  heat  in  presence  of  the  lime  and  goes  to  the 
lime,  forming  carbonate  of  lime. 

The  metals  which  will  decompose  water  without  applying 
heat  are  calcium,  strontium,  barium,  sodium  and  potassium — 
the  same  uniting  with  oxygen  of  the  water  and  liberating  hydro- 
gen. The  products  formed  are  the  oxides  of  the  metals.  Any 
metals  decompose  water  if  they  form  the  terminal  of  an  electric 
circuit  and  are  dipped  into  the  water.  Decomposition  is  has- 
tened by  adding  an  acid  to  the  water.  Very  intense  heat  will 
decompose  steam.  If  iron  or  other  easily  oxidizable  metal  is  in 
contact  with  the  steam,  the  oxide  of  that  metal  is  formed. 

One  of  the  most  important  characteristic  differences  between 
physical  and  chemical  changes  is  that  whereas  in  a  chemical 
change  the  bodies  subjected  to  the  change  have  different  chem- 
ical and  physical  properties  after  the  change  ;  while  before  and 
after  a  physical  change  the  bodies  have  the  same  physical  and 
chemical  properties  except,  sometimes,  as  to  degree.  Illustra- 
tration  :  Chemically  change  iron  by  burning  it  until  it  is  iron 
rust — /.  e.,  ferric  oxide.  Although  the  iron  is  still  in  the  ferric 
oxide,  yet  the  oxide  has  none  of  the  characteristics  of  iron  nor 
of  oxygen ;  for  example,  iron  is  magnetic,  its  rust  is  non-mag- 
netic ;  iron  has  a  metallic  lustre,  its  oxide  has  none.  Iron  is 
nearly  eight  times  as  heavy  as  water,  while  its  oxide  is  only 
slightly  heavier.  Iron  has  a  different  color  from  its  oxide.  But 
suppose  a  physical  change  is  produced  in  iron,  it  still  remains 
iron.  Suppose  it  undergoes  the  physical  change  of  being 


60 

melted,  it  is  still  iron,  and  has  the  important  chemical  and  phy- 
sical properties  of  iron.  Chemical  changes  are  thus  distinguish- 
able from  physical  changes. 

Elements  differ  from  compounds  in  being  non-decomposable, 
and  compounds  from  mixtures  as  having  different  chemical  and 
physical  properties  from  the  elements  of  which  it  is  made,  while 
a  mixture  is  made  of  elements  or  compounds  which  have  no 
chemical  union  but  still  possess  the  properties  of  its  con- 
stituents. 

The  metallic  elements  are  aluminium,  Al  II  ;  antimony,  Sb 
III ;  arsenic,  As  III;  barium,  Ba  II;  bismuth,  Bi  III;  cadmium, 
Ca  II;  caesium,  Cs  I;  calcium,  Ca  II;  cerium,  Ce  II;  chromium, 
Cr  II;  cobalt,  Co  II;  copper,  Cu  II;  didymium,  D  II;  erbium, 
E;  glucinum,  Gl;  gold,  Au  III;  indium,  In  II;  uridium,  Ir  IV; 
iron,  Fe  II;  lanthanum,  La  II;  lead,  Pb  II;  lithium,  Li  I;  mag- 
nesium, Mg  II;  manganese,  Mn  II;  mercury,  Hg  II;  molyb- 
denum, Mo  VI;  nickel,  Ni  II;  niobium,  Nb  V;  osmium,  Os  IV; 
palladium,  Pd  II;  platinum,  Pt  II;  potassium,  K  I;  rhodium, 
Rh  II;  rubidium,  Rb  I;  ruthenium,  Ru  I;  silver,  Ag  I;  sodium, 
Nal;  strontium,  Sr  II;  tantalum,  TaV;  thallium,  Tl  I;  thorium, 
Th  IV;  tin,  Sn  IV;  titanium,  Ti  IV;  tungsten,  W  VI;  uranium, 
U  III;  vanadium,  V  III;  yttrium,  Y  II;  zinc,  Zn  II;  zirconium, 
Zr  IV. 

The  non-metallic  elements  are  boron,  B  III;  bromine,  Br 
I;  carbon,  C  IV;  chlorine,  Cl  I;  fluorine,  F  I;  hydrogen,  H  I; 
iodine,  I  I;  nitrogen,  N  III;  oxygen  O  II;  phosphorus,  P  III; 
selenium,  Se  II;  silicon,  Si  IV;  sulphur,  S  II;  tellurium,  Te  II. 
The  meaning  of  the  numerals  and  abbreviations  is  given 
later. 

The  general  distinguishing  characteristics  of  metals  are  their 
fusibility,  hardness,  ductility,  comparatively  heavy  weight.  They 
can  be  welded,  they  have  an  appearance  always  recognizable, 
and  are  good  conductors  of  heat  and  electricity. 

The  composition  of  well-known  alloys  are  explained  thus  : 
Copper  and  zinc  make  brass  ;  lead  and  tin,  solder  and  pewter  ; 
copper  and  tin,  gun  speculum  and  bell  metal;  twenty-two  parts 
of  gold  to  two  parts  of  copper,  standard  gold;  mercury  and 
another  metal,  amalgam ;  bismuth  and  another  metal,  fusible 
metal;  bismuth,  five  parts;  tin,  two  parts;  lead,  three  parts,  an 
alloy  fusible  in  boiling  water;  antimony  and  lead,  type  metal. 
Zinc,  tin,  lead  and  cadmium  impart  to  their  own  alloys  their 
own  peculiar  properties  in  proportion  to  the  amounts  contained 
in  the  alloys.  Other  metals  do  not  impart  their  properties  to 
their  alloys  in  the  proportion  in  which  they  exist  in  the  alloys. 
The  specific  gravity  and  coefficient  of  expansion  of  the  alloys 


61 

containing  two  or  more  of  the  metals  lead,  tin,  zinc  and  cadmium 
are  the  average  of  those  of  the  metals  forming  the  alloy.  Other 
properties,  as,  for  example,  the  fusing  point,  vary  from  those  of 
the  constituents  of  the  alloy.  The  fusing  points  of  tin,  bismuth, 
cadmium  and  lead  are  respectively  235°,  270°,  315°  and  334°  Q, 
while  their  alloy  fuses  at  65°.  It  is  a  peculiar  coincidence  that 
mixtures  of  certain  salts  melt  at  a  lower  temperature  than  the 
average  of  its  constituents.  Illustration  :  Potassic  and  sodic 
carbonates  when  mixed  fuse  at  a  much  lower  temperature  than 
either  would  alone.  The  same  is  true  of  the  chlorides  of  those 
metals.  The  alloys  of  the  said  metals,  lead,  tin,  zinc  and  cad- 
mium, with  each  other  have  electric  and  heat-conducting  powers, 
which  are  directly  proportional  to  the  proportions  in  which  they 
exist,  but  this  is  not  true  of  the  alloys  of  the  other  metals. 
Copper  is  soft,  but  with  the  addition  of  a  little  zinc  it  becomes 
hard.  Sometimes  an  alloy  is  soluble  in  an  acid,  while  one  of  its 
constituents  is  not.  This  is  the  case  with  an  alloy  of  silver  and 
platinum,  which  is  soluble  in  boiling  nitric  acid,  while  platinum 
by  itself  is  not  acted  upon  at  all.  On  the  other  hand,  an  alloy 
of  gold  and  silver  is  not  soluble  in  nitric  acid,  but  silver  by  itself 
is  soluble. 

The  combination  of  the  elements  with  one  another  and  in 
different  proportions  form  hundreds  of  compounds. 

An  example  of  a  mixture  is  that  of  wax  and  sand.  Each 
retains  its  own  properties.  By  mixing  different  elements  or 
compounds  together  the  result  is  a  mixture  or  compound  accord- 
ing to  whether  a  substance  has  been  formed  which  has  different 
properties  from  any  of  its  constituents. 

Liquids  and  gases  will  gradually  mix  together,  even  if 
separated  by  a  porous  membrane,  and  a  peculiar  action 
is  that  the  denser  will  pass  through  as  much  slower  as  it 
is  denser. 

Chemicals  unite  to  form  compounds  because  there  exists  a 
force  of  attraction  among  the  elements.  This  attraction  differs 
from  cohesion  or  adhesion  in  that  it  does  not  exist  between  the 
atoms  of  the  same  element  nor  between  the  molecules  of  the 
same  compound.  Thus,  a  piece  of  lead  has  cohesion  among  its 
atoms,  holding  them  together.  It  has  also  adhesion  because 
another  piece  of  lead  is  held  by  it,  but  it  has  no  chemical  attrac- 
tion for  its  own  atoms.  Chemical  attraction  exists  only  between 
atoms  or  molecules  of  different  kinds  of  substances.  Thus,  in 
paper,  oxygen,  hydrogen  and  carbon  are  so  strongly  and  inti- 
mately held  together  that  howsoever  finely  the  paper  may  be 
subdivided  by  a  knife  or  other  mechanical  means  these  elements 
do  not  separate. 


62 

The  less  the  cohesion  the  greater  the  effects  of  chemical 
attraction.  Thus,  in  liquids  the  cohesion  is  least  and  molecular 
repulsion  is  least,  and  in  the  liquid  condition  compounds  gene- 
rally are  most  easily  formed,  as  illustrated  by  solid  calcic  chlor- 
ide and  ammonic  fluoride,  which  do  not  combine  in  the  solid 
state,  but  they  do  if  first  dissolved  in  water.  A  powder  sepa- 
rates from  the  water  and  is  found  to  be  calcic  fluoride.  The 
fluoride  leaves  the  ammonia  and  combines  with  the  calcium. 

The  chemical  attraction  is  sometimes  so  strong  that  solids 
combine  directly,  being  so  powerful  that  the  atoms  of  either 
body  overcome  the  cohesion  in  the  other  body.  Thus,  sal 
ammoniac  (ammonic  chloride)  and  lime  are  both  solid  and  have 
no  odor.  Let  them  be  mixed  together,  immediately  the  smell 
of  ammonia  is  very  strong.  The  atoms  of  the  lime  unite  with 
some  of  those  of  the  chloride,  liberating  the  ammonia  gas,  which 
gives  the  odor.  Again,  a  bright  fire  is  obtained  by  simply 
touching  together  solid  iodine  and  solid  phosphorus.  The 
smoke  consists  of  phosphoric  iodide.  The  atoms  of  the  phos- 
phorus and  iodine  separate  from  each  other  in  each  solid  and 
come  together  again  in  such  a  manner  that  each  atom  of  phos- 
phorus takes  three  atoms  of  iodine,  making  one  molecule  of 
phosphoric  iodide. 

It  is  a  curious  principle  that  if  substances  are  soluble  in 
water  or  acids  they  will  combine  if  the  compounds  are  such  as 
to  be  insoluble  in  the  liquid.  Dissolve  aluminic  sulphate  in 
water.  Add  a  solution  of  ammonia  in  water.  A  white  powder 
is  formed,  which  does  not  dissolve,  and  which  is  found  to  be  a 
new  compound,  consisting  of  aluminic  oxide,  which  is  called  a 
precipitate,  because  it  falls  to  the  bottom  of  the  vessel. 

Sometimes  two  solutions  of  two  compounds  when  mixed 
result  in  two  insoluble  compounds,  with  nothing  remaining  in 
solution.  Mix  together  solutions  of  argentic  sulphate  and 
baric  chloride.  The  precipitates  are  baric  sulphate  and  argentic 
chloride.  When  filtered,  the  solution  contains  nothing,  unless 
an  excess  of  one  compound  exists.  Any  given  free  element 
unites  with  one  or  more  free  elements  at  fixed  temperatures, 
differing  according  to  the  particular  elements. 

Illustration  :  Hydrogen  and  oxygen  unite  at  about  the  tem- 
perature of  1,000°  F.  in  the  case  where  each  is  isolated  from 
other  elements.  Above  that  temperature  they  will  not  unite. 
The  heat  causes  the  repulsion  between  the  atoms  to  be  stronger 
than  the  chemical  attraction.  Below  that  temperature  they  will 
not  separate,  because  the  chemical  attraction  is  greater  than  the 
repulsion  due  to  heat.  About  the  only  exception  is  that  of 
chlorine  and  hydrogen,  which  have  two  temperatures  or  kind- 


ling  points.  In  the  dark  a  very  high  temperature  is  required  to 
cause  them  to  unite,  while  in  diffused  daylight  they  are  kindled 
at  approximately  the  ordinary  atmospheric  temperature.  There 
is  no  reason  to  believe  that  the  same  amount  of  work  is  not 
done  ;  for  with  a  high  temperature  the  union  is  instantaneous, 
while  with  diffused  daylight  (not  in  the  sun)  a  long  time  is  con- 
sumed— the  action  is  slow  but  long.  If  the  oxygen  and  hydro- 
gen are  associated  with  other  compounds,  they  often  unite  at 
approximately  the  ordinary  temperature.  Thus  in'  the  decay  of 
wood,  oxygen  and  hydrogen  leave  the  carbon  and  form  water. 
Again,  when  sulphuric  acid  acts  upon  sugar,  the  hydrogen  and 
oxygen  leave  the  sugar  at  about  120°  F.  in  the  proportion  to 
form  water  and  unite  with  the  sulphuric  acid,  which  becomes 
more  dilute.  The  principles  are,  therefore  :  (tf)  That  isolated 
elements  unite  at  a  fixed  temperature,  which  depends  upon  what 
the  elements  are.  The  temperatures  vary  all  the  way  from  the 
ordinary  temperature  to  many  hundred  degrees.  (£)  Elements 
already  combined  leave  one  ar  other  to  join  foreign  elements 
alone  or  compound  at  a  lower  temperature  than  that  at  which 
they  would  combine  if  isolated.  How  many  hundreds  of  com- 
pounds are  formed  by  this  principle! 

Howsoever  finely  substances  are  mechanically  pulverized, 
chemical  action  is  not  generally  facilitated,  as  it  is  when 
the  substances  are  dissolved.  An  exception  is  that  of 
sulphur  and  potassic  chlorate.  Pulverize  them  finely  and 
mix  intimately.  Suddenly  they  combine  with  a  dangerous 
explosion. 

Hydrogen  and  oxygen  always  combine  in  fixed  proportions 
by  volume  to  form  water.  One  gallon  of  oxygen  combines  with 
two  gallons  of  hydrogen.  With  different  proportions,  a  residue 
of  one  of  the  gases  is  found.  Hydrogen  and  chlorine  combine 
in  the  proportion  of  one  volume  of  each  to  form  hydric  chloride. 
Any  given  compound  is  always  and  only  formed  by  the  com- 
bination of  the  elements  in  a  fixed  proportion.  However,  ele- 
ments often  combine  in  different  proportions,  but  the  com- 
pounds are  different.  Thus  nitrogen  and  oxygen  combine  in 
five  different  proportions  by  volume.  One  volume  of  hydrogen 
can  unite  with  one  or  two  or  three,  etc.,  volumes  of  many  other 
elements  and  compounds. 

What  is  true  of  combining  volumes  is  true  of  combining 
weights;  elements  or  compounds  combine  in  different  propor- 
tions by  weight  ;  but  the  same  proportional  weights  always  pro- 
duce the  same  compound.  A  few  important  exceptions  exist. 
Starch  and  dextrine  have  equal  weights  of  each  of  its  elements. 
Each  has  6  parts  of  carbon,  10  of  hydrogen  and  5  of  oxygen. 


64 

Although  having  exactly  the  same  chemical  composition,  starch 
and  dextrine  have  different  physical  properties. 

A  few  exceptions  exist  also  as  to  atoms  of  the  same  sub- 
stance combining  with  each  other.  One  atom  of  oxygen  can  be 
made  to  combine  with  another  atom  of  oxygen,  whereby  ozone 
is  formed.  The  difference  between  the  element  and  its 
compound  is  that  whatever  property  oxygen  has,  ozone  has  the 
same  magnified.  Thus  oxygen  bleaches  very  slowly  ;  ozone 
bleaches  rapidly. 

Elements  which  are  free  may  combine  to  form  compounds. 
It  is  also  true  that  the  elements  of  one  compound  will  often 
depart  and  combine  with  the  elements  of  another  compound,  or 
with  other  free  elements.  Potassium  will  combine  with  free 
oxygen,  or  it  will  take  oxygen  from  water.  In  both  cases 
potassic  oxide  is  formed. 

How  is  it  known  that  a  chemical  change  occurs  ?  By  change 
of  color,  of  form,  of  temperature  or  production  of  electricity. 
Gunpowder  when  exploded  changes  from  the  solid  to  the  gaseous 
form.  Sulphuric  acid  added  to  copper  produces  a  blue  sub- 
stance— cupric  sulphate  Silver  and  copper  placed  on  the 
tongue  and  brought  in  contact  with  the  terminals  of  a  delicate 
galvanometer  are  found  to  deflect  the  needle.  Sulphuric  acid 
added  to  syrup  produces  heat.  In  all  these  cases  new  com- 
pounds are  formed. 

Compounds  which  at  the  same  time  are  sour  to  the  taste, 
which  turn  blue  litmus  paper  red,  which  are  composed  of  non- 
metals,  and  which  contain  hydrogen,  are  acids  ;  those  acids 
which  contain  hydrogen  only  are  called  hydracids.  Those 
which  contain  hydrogen  and  oxygen  are  oxacids.  An  acid  is  in 
nearly  every  case  a  combination  of  either  oxygen  and  hydrogen 
or  hydrogen  alone  with  a  non-metal.  When  an  acid  is  named, 
therefore,  the  above  rule  enables  one  to  name  its  constituents. 
Thus,  bromic  acid  contains  oxygen,  hydrogen  and  bromine. 
Hydro  fluoric  acid  contains  hydrogen  and  fluorine. 

Non-acids,  called  hydrates,  and  formerly  called  alkalis,  have 
opposite  properties  from  those  of  acids,  since  they  turn  red 
litmus  paper  blue;  have  a  caustic  taste;  and  are  composed  of 
hydrogen,  oxygen  and  a  metal,  while  acids  do  not  contain  a  metal. 

Hydrates  are  named  in  such  a  manner  that  their  composi- 
tions are  apparent  Thus,  baric  hydrate  is  the  combination  of 
hydrogen  and  oxygen  with  the  metal  barium;  ferric  hydrate  has 
hydrogen,  oxygen  and  iron,  and  calcic  hydrate  has  hydrogen, 
oxygen  and  calcium. 

There  are  two  hydrates  of  iron,  the  fernV  and  the  f enw/.y,  the 
latter  containing  less  oxygen,  and  so  with  some  other  metals. 


65 

Instead  of  speaking  of  silver  hydrate,  iron  hydrate,  &c.,  the 
Latin  words  are  used  for  the  sake  of  euphony  and  system,  but  in 
many  the  English  is  adhered  to,  as  in  cobaltic  hydrate,  meaning 
that  hydrate  which  contains  cobalt. 

If  calcic  hydrate  is  heated,  all  the  hydrogen  and  enough 
oxygen  escape  to  form  water  (/.  e.,  one  part  of  oxygen  to  every 
two  of  hydrogen.)  The  remainder  is  calcic  oxide.  So  with 
other  hydrates.  They  may  be  reduced  similarly  to  oxides,  not 
necessarily  by  heat;  but  that  product  which  is  left  by  removing 
all  the  hydrogen  and  enough  oxygen  to  form  water  is  the  oxide 
of  the  metal.  The  oxides  are  so  named  that  their  constituents 
are  apparent.  Thus,  chromic  oxide  is  composed  of  the  metal 
chromium  and  oxygen.  Auric  oxide  has  gold  and  oxygen. 
Zincic  oxide  has  zinc  and  oxygen.  When  two  oxides  of  the 
same  metal  occur,  the  suffixes  ic  and  ous  are  used  as  before,  but 
sometimes  there  are  three  oxides  of  the  same  metal.  Recourse 
is  then  had  to  the  prefixes  man,  meaning  one  part  of  oxygen;  di, 
meaning  two  parts,  and  tri,  meaning  three  parts.  Chromic 
trioxide  has  three  parts  of  oxygen,  while  chromic  monoxide  has 
one  part. 

Metallic  oxides  need  not  always  be  made  by  removing  hy- 
drogen and  some  of  the  oxygen  from  hydrates.  Thus,  potassic 
oxide  may  be  formed  by  burning  potassium  in  dry  air,  but  the 
result  as  far  as  the  proportions  of  the  elements  in  the  oxide  are 
concerned  is  the  same  as  if  formed  from  hydrates  in  the  man- 
ner set  forth. 

Acids  turn  blue  litmus  paper  red.  Hydrates  turn  red  litmus 
blue.  There  is  a  third  class  of  compounds  which  will  neither 
turn  red  litmus  blue,  nor  blue  litmus  red,  nor  will  it  have  any 
coloring  effect  upon  litmus;  neither  does  it  have  any  acid  or 
burning  taste.  They  are  called  neutral  compounds.  The  com- 
bination of  a  metal  with  a  non-metal  forms  a  neutral  compound. 
The  name  distinguishes  the  constituents.  Thus,  manganic 
chloride  has  manganese  and  chlorine.  Ide  is  the  suffix.  Ide  is 
used  to  indicate  a  neutral  binary  compound. 

Exceptions:  Some  oxides  of  non-metals  are  neutral. 
Example:  Water,  carbonic  oxide,  nitric  oxide,  and  a  very  few 
others. 

The  hydrogen  in  an  acid  may  be  replaced  in  part  or  wholly 
by  a  metal.  Thus,  in  sulphuric  acid  (an  oxacid)  the  hydrogen 
can  be  replaced  by  zinc,  whereby  the  compound  is  changed  to 
zincic  sulphate.  The  name  given  to  a  compound  thus  obtained 
is  called  a  salt.  Common  salt  (sodic  chloride)  may  be  formed 
by  adding  sodium  to  the  hydracid,  called  hydric  chloride.  The 
sodium  expels  the  hydrogen  and  unites  with  the  chlorine.  Where 


66 

the  oxacid  is  used  the  word  ends  in  ate  or  tte,  according  as  to 
whether  there  is  more  or  less  oxygen.  If  made  from  a  hydracid, 
the  word  ends  in  tde,  as  in  the  formation  of  the  names  of  neutral 
binary  compounds.  Examples  of  the  formation  of  salts:  Silver 
added  to  the  oxacid  nitric  acid  results  in  argentic  nitrate;  iron 
added  to  the  oxacid  sulphuric  acid  forms  ferric  sulphate.  Lead 
added  to  the  hydracid,  hydric  chloride,  forms  plumbic 
chloride. 

Some  substances  in  chemistry  have  unsystematic  names  and 
greatly  hinder  the  growth  of  the  science,  as  system  and  regu- 
larity are  prevented.  Some  are  named  after  men,  as  Glauber 
salts.  The  proper  name  is  sodic  sulphate,  which  by  its  very 
name  shows  its  own  composition.  Oil  of  vitriol  is  sulphuric 
acid.  Saltpeter  is  potassic  nitrate.  Soda  is  sodic  oxide.  Pot- 
ash is  potassic  hydrate.  Sulphuretted  hydrogen  is  hydric 
sulphide.  . 

Oxacids,  hydracids,  anhydrides,  hydrates,  neutral  binary 
compounds,  and  salts  are  indicated  not  only  as  to  their  com- 
position by  their  names,  but  also  by  symbols  containing  figures 
which  indicate  the  propotional  amounts  of  the  elements  in  the 
compound.  For  the  sake  of  brevity,  initials  of  the  names  of  the 
elements  are  employed.  Sometimes  the  initial  of  the  Latin 
word  is  used,  so  that  the  same  letter  for  different  elements  may 
be  avoided.  Thus,  H2SO4  is  an  oxacid,  called  sulphuric  acid. 
The  figures  2  and  4  show  that  there  are  two  parts  by  weight  and 
volume  of  hydrogen  and  four  of  oxygen.  S  has  no  number,  but 
one  part  of  sulphur  is  understood.  These  symbols  are  very  use- 
ful in  showing  the  reactioms  between  compounds.  Thus  Zn  + 
H2SO4  =  H2  +  ZnSO4. 

The  metal  zinc  replaces  hydrogen  in  the  oxacid  and  changes 
it  to  the  salt,  zincic  sulphate.  To  show  the  composition  of 
water,  the  equation  is  thus  : 

H2  +  O  =  H2O. 

To  show  how  an  oxacid  is  turned  into  an  anhydride,  this 
equation  is  an  example: 

H2SO4  — H2O=  SO3  (sulphuric  anhydride.) 

The  following  equation  shows  how  a  hydrate  is  changed  to  a 
metallic  oxide: 

2KHO  (Potassic  hydrate)  —  H2O  =  K2O. 

Some  elementary  atoms  have  the  power  of  combining  with  i 
atom  of  hydrogen,  some  with  2,  some  with  3,  and  some  with  4, 
5  or  6.  Illustration:  In  HC1  (hydric  chloride)  i  atom  of 
chlorine  is  combined  with  i  of  hydrogen.  In  H2O  (water,)  i 
atom  of  oxygen  is  combined  with  2  of  hydrogen.  In  £[3,  N 
v ammonia)  i  atom  of  nitrogen  is  combined  with  3  of  hydrogen. 


67 

In  H^-C  (marsh  gas)  i  atom  of  carbon  is  combined  with  4  of 
hydrogen. 

That  elementary  substance  whose  i  atom  combines  with  i  of 
hydrogen  is  termed  a  monad,  from  the  Greek  for  unity.  Sim- 
ilarly those  which  take  up  2,  3,  4  atoms  of  hydrogen  are  called 
dyads,  triads  and  tetrads  respectively. 

It  is  a  principle  that  i  atom  of  a  monad  will  combine  with 
i  atom  of  another  monad;  that  2  atoms  of  a  monad  will  com- 
bine with  i  atom  of  a  dyad,  or  2  atoms  of  another  monad;  that 

3  atoms  of  a  monad  will  combine  with  i  atom  of  a  triad,  or  with 
i  atom  of  a  dyad  and  i  of  a  monad,  or  with  3  atoms  of  a  monad, 
and  so  on  in  the  arithemtical  manner.  So  also  with  dyads.    One 
atom  takes  2  monads,  or  i  dyad.  Two  atoms  of  a  dyad  take  4  of  a 
monad,  or  i  monad  and  i  triad,  &c.      In  this  manner  it  is  only 
necessary  to  know  whether  an  atom  is  a  monad,  dyad,  triad,  &c., 
in  order  to  know  the  proportional  amounts  of  elements   in  any 
given  compound  whose  elements  are  known,  and  to  be  able  to 
write  the  symbols  of  compounds  and  to  foreknow  the  new  com- 
pounds which  will  be  formed  in  any  chemical  changes. 

The  monad,  dyad,  triad,  &c.,  elements  are  indicated  by  the 
Roman  numerals  found  after  the  names  of  the  elements  hereto- 
fore given. 

A  dyad  may  replace  2  monads,  a  triad,  3  monads,  or  i 
monad  and  i  dyad,  &c.  Thus,  in  H2O  the  dyad  oxygen  may 
be  replaced  by  2  atoms  of  the  monad  chlorine,  making  the  com- 
pound which  is  equal  to  2H  Cl. — /.  «?.,  two  molecules  of  hydric 
chloride.  CH4  is  one  of  the  important  constituents  of  coal 
gas.  The  tetrad  C  (carbon)  may  unite  with  2  atoms  of  the  dyad 
oxygen,  which  will  replace  4  atoms  of  the  monad  hydrogen.  The 

4  atoms  of  the  monad  hydrogen  will  also  unite  with  2  atoms  of 
the  dyad  oxygen,  forming  water.     The  following  equation  shows 
the  reactions,  assuming  that  the  supply  of  oxygen  is  plentiful: 

CH4+  04  =  CO2  +  2  H2O. 

This  is  just  what  happens  when  marsh  gas  (CH4)  is  burned 
in  air.  Carbonic  di-oxide,  CO2,  and  water,  H2O,  are  formed. 
Similarly  any  reactions  can  be  predicted.  Suppose  that  zinc  is 
added  to  hydric  chloride.  Zinc  is  a  dyad,  therefore  the  equa- 
tion is: 

Zn  +  2  HC1  =  Zn  Cla  -f  H2. 

It  is  known  that  there  should  be  2  molecules  of  H  Cl,  because 
Zn  must  have  2  atoms  of  the  monad  Cl  in  order  to  be  satisfied. 

Sometimes  compounds  exist  which  are  not  "satisfied  "  ;  but 
they  are  unstable;  they  become  satisfied  when  opportunity 
offers.  Thus,  if  carbon  is  burned  in  a  limited  supply  of  oxygen 
the  lower  oxide,  CO,  is  formed.  Since  C  is  a  tetrad  and  O  is  a 


68 

dyad,  the  compound  is  not  satisfied.  The  carbon  can  take  up 
another  atom  of  oxygen,  and  experiment  shows  that  it  does  so 
when  the  CO  is  burned  in  air,  whereby  carbon  di-oxide,  CO2, 
is  formed.  CO  is  one  of  the  constituents  of  coal  gas,  being 
combustible,  while  CO 2  is  one  of  the  gases  escaping  from  a  gas 
flame. 

Some  reactions  are  given  below  employing  the  above  prin- 
ciples. 

Na  (Sodium,  monad)  +  H2O  =  H  Na  O  +  H. 
The  above  is  the  reaction  when  metallic  sodium  is  placed 
upon  water.     The  products    are  sodic  hydrate    and   hydrogen. 
Fe  (iron)  +  H2S  04  =  Fe  S  04  +  2H. 
In  the  above,  the  dyad  Fe  takes  the  place  of  2  atoms  of  the 
monad  H  in  the  compound  H2SO4. 

Ca  CO3  (calcic  carbonate)  +  Na2S    (sodic  sulphide).  = 
Na  2.  COs  (sodic       "         )  +  Ca  S       (calcic        "       ). 
Two  atoms  of  the  monad  sodium  change  places  with  i  atom 
of  the  dyad  Ca. 

The  following  compounds  of  metals  are  more  or  less  soluble 
in  water  : 

Acetates,  except  that  of  calcium;  chlorates;  chlorides,  except 
those  of  mercurosum  and  silver;  formates;  iodides,  except  that 
of  silver;  nitrates;  sulphates,  except  those  of  antimony,  barium 
lead  and  strontium;  fluoride,  except  those  of  barium,  calcium, 
copper,  lead,  magnesium,  manganese  and  strontium;  benzoate, 
except  those  of  copper,  tetrad,  iron,  lead,  mercurosum;  bromide, 
except  those  of  mercurosum  and  silver;  citrate,  except  those  of 
barium,  cadmium,  lead,  manganese,  mercurosum,  silver  and 
strontium;  ferrocyanide,  except  those  of  cobalt,  dyad,  iron,  man- 
ganese, nickel,  silver  and  zinc;  malate,  except  that  of  mercu- 
rosum; succinate,  except  those  of  lead,  mercurosum,  silver  and 
tetrad  tin;  tartrate,  except  those  of  antimony,  barium,  bismuth, 
calcium,  lead,  mercuricum,  nickel,  silver,  strontium,  dyad,  tin 
and  zinc;  arseniate  of  ammonium,  of  potassium  and  sodium; 
arsenite  of  ammonium,  of  potassium  and  of  sodium;  borate  of 
ammonium,  of  cadmium,  of  magnesium,  of  potassium  and  of 
sodium;  carbonate  of  ammonium,  of  potassium  and  of  sodium; 
chromate  of  ammonium,  of  calcium,  of  copper,  of  tetrad  iron, 
of  magnesium,  of  mercuricum,  of  nickel,  of  potassium,  of  sodium 
and  of  zinc;  cyanide  of  ammonium,  of  barium,  of  calcium,  of 
magnesium,  of  mercuricum,  of  potassium,  of  sodium,  of  strontium ; 
ferrocyanide  of  ammonium,  of  barium,  of  calcium,  of  magnesium, 
of  potassium,  of  sodium  and  of  strontium;  hydroxide  of  am- 
monium, of  barium,  of  calcium,  of  potassium,  of  sodium  and  of 
strontium;  oxalate  of  ammonium,  of  chromium,  of  manganese 


of  potassium,  of  sodium  and  of  tetrad  tin;  oxide  of  barium,  of 
calcium,  of  potassium,  of  sodium  and  of  strontium;  phosphate 
of  ammonium,  of  antimony,  of  barium,  of  calcium,  of  potassium, 
of  sodium;  silicate  of  potassium  and  of  sodium;  sulphite  of 
ammonium,  of  barium,  of  calcium,  of  potassium,  of  sodium  and 
of  strontium;  aluminium  ammonium  sulphate;  aluminium  po- 
tassium sulphate ;  ammonium  arsenic  chloride  ;  ammonium 
sodium  phosphate  ;  ammonium  ferrous  sulphate  ;  ammonium 
cupric  sulphate;  ammonium  potassium  tartrate;  antimony  po- 
sassium  tartrate;  chromic  potassium  sulphate;  iron  (ferric)  po- 
tassium tartrate;  platinic  bromide,  chloride  and  cyanide,  nitrate, 
oxalate  and  sulphate. 

The  following  compounds  of  metals  are  more  or  less  soluble 
in  one  or  more  of  the  acids,  nitric  (HNOs),  sulphuric  (H2SO4) 
and  hydrochloric  (H  Cl) : 

Arzeniates,  except  those  of  ammonium,  potassium  and  so- 
dium; arsenites,  except  those  of  ammonium,  potassium  and 
sodium;  borates,  except  those  of  ammonium,  potassium  and 
sodium;  carbonates,  except  those  of  potassium  and  sodium; 
chromates,  except  those  of  ammonium,  copper,  tetrad  iron, 
magnesium,  nickel,  potassium  and  sodium;  cyanides,  except 
those  of  ammonium,  calcium,  magnesium,  mercuricum,  potas- 
sium, sodium  and  strontium;  hydroxides,  except  those  of  am- 
monium, barium,  potassium,  sodium  and  strontium;  oxalates, 
except  those  of  ammonium,  potassium,  sodium  and  tetrad  tin; 
oxides,  except  those  of  barium,  potassium,  sodium  and  strontium; 
silicates,  except  those  of  potassium  and  sodium  ;  sulphides, 
except  those  of  ammonium,  barium,  potassium,  sodium  and 
strontium;  tartrates,  except  those  of  aluminium,  ammonium, 
chromium,  cobalt,  copper,  tetrad  iron,  potassium  and  sodium; 
phosphates,  except  those  of  ammonium,  potassium,  sodium ; 
acetate  of  calcium  and  of  mercurosum;  benzoates  of  copper, 
tetrad  iron,  lead,  of  mercurosum,  mercuricum,  silver;  bromides 
antimony,  bismuth,  mercurosum,  silver;  chlorides  of  antimony, 
bismuth,  mercurosum  ;  citrates  of  barium,  cadmium,  calcium, 
lead,  manganese,  mercurosum,  mercuricum,  silver,  strontium, 
zinc;  cyanides  of  barium,  cadmium,  chromium,  cobalt,  copper, 
dyad  iron,  lead,  manganese,  nickel,  zinc;  ferrocyanides  of  lead, 
zinc;  ferrocyanides  of  barium,  lead,  manganese,  and  of  zinc; 
fluorides  of  barium,  cadmium,  cobalt,  copper,  dyad  iron,  lead, 
magnesium,  manganese,  mercuricum,  nickel,  strontium,  and  of 
zinc;  formates  of  lead;  iodides  of  antimony,  bismuth,  lead, 
mercurosum,  mercuricum;  malates  of  barium,  calcium,  lead, 
mercurosum,  mercuricum,  and  silver;  succinates  of  aluminium, 
barium,  calcium,  cobalt,  of  copper,  of  lead,  of  mercurosum,  of 


70 

silver,  of  strontium,  tetrad  tin,  and  zinc;  ammonium  magnesium 
phosphate;  antimony  oxychloride;  bismuth  oxychloride;  bismuth 
basic  nitrate ;  calcic  sulphantimonate  ;  mercurius  solubilis 
Hahnemanni;  mercurammonium  chloride;  mercuric  sulphate, 
basic;  potassium  platinic  chloride. 

The  following  compunds  of  metals  are  among  those  which 
are  insoluble  in  the  acids  above  named: 

Chloride  of  silver;  cyanide  of  silver;  ferricyanide  of  cobalt, 
of  dyad  iron,  of  manganese,  of  nickel  and  of  silver;  ferrocyanide 
of  cobalt,  of  copper,  of  dyad  iron,  of  tetrad  iron,  of  nickel,  of 
silver;  iodide  of  silver;  sulphate  of  strontium. 

It  is  a  very  peculiar  phase  of  combination  that  certain  atoms 
of  different  elements  change  place  from  one  compound  to 
another  and  have  a  fixed  proportion  for  combining.  The  prin- 
cipal compounds  of  this  class  are  stated  thus,  with  the  proper 
word,  monad,  dyad,  &c.,  to  indicate  their  power  of  combining 
with  other  monads,  dyads,  &c.: 

NH4,  monad,  is  a  root  of   ammonia   compounds.     Example: 
(NH4.)  Cl  (ammonic  chloride). 

NOs,  monad,  is  a  root  of  nitrates.   Example:  Ca  (NO3)2  (calcic 
nitrate). 

CO3,  dyad,  is  a  root  of  carbonates.     Example:    Ba  (COs). 

SO4,  dyad,  is  a  root  of  sulphates.     Example:  Cu  864  (cupric 
sulphate). 

HO,  monad,  is  a   root  of  hydrates.     Example:  KHO  (potassic 
hydrate). 

CN,  monad,  forms  the  root  of  cyanides. 

PO4,  a   triad,  forms   the  root  of  phosphates.     Example:  Hg3 
(PO4)2  (mercuric  phosphate). 

Any  one  of  these  roots  will  go  from  one  compound  to  another 
in  certain  reactions  without  themselves  appearing  to  undergo 
any  decomposition.  Example:  Cu  +  H2(SO4)  —  H2  +  Cu  (804). 

The  operation  is  that  when  copper  is  dissolved  in  sulphuric 
acid  (£[2804),  the  root  (864)  goes  from  the  zinc  to  the  copper 
and  the  hydrogen  is  set  free.  It  is  another  wonderful  freak, 
that  these  roots  never  exist  by  themselves,  unless  that  infinitesi- 


71 

mal  time  taken  in  passing  from  one  compound  to  another  be 
considered  ;  but  by  losing  or  gaining  another  atom  of  one  of  the 
elements,  they  exist  alone.  Example: 

Taking  H  from  NH4  leaves  NH3  (ammonia). 

"       O     "       SO4       "       SO3  (sulphurous  acid). 

"       O     "       CO3       "       COz   (carbonic  di-oxide). 
Adding  H  to  HO  gives  H2O  (water). 

The  gist  of  practical  chemistry  is  that  relating  to  an  accurate 
and  extended  knowledge  of  the  reactions  which  occur  among 
chemical  compounds.  One  should  follow  the  equations  below, 
taking  notice  of  the  exact  composition  of  each  chemical,  and 
how  the  foregoing  principles  have  been  applied.  In  order  to 
make  the  equations  easily  intelligible,  the  name  of  the  com- 
pound often  accompanies  the  symbol.  The  compounds  on  the 
left  undergo  an  exchange  of  some  of  their  elements,  and  two  or 
more  new  compounds  are  formed,  according  to  the  rules  already 
stated.  One  of  the  new  compounds  is  generally  a  precipitate 
— /'.  e.,  one  of  the  new  compounds  is  insoluble  and  falls  as  a 
powder  to  the  bottom  of  the  vessel  and  may  be  obtained  free 
by  filtration.  An  assistance  in  this  respect  will  be  the  list  of 
soluble  and  insoluble  compounds  already  given.  Sometimes  the 
new  compound  or  liberated  element  is  a  gas  and  escapes  into 
the  air  or  into  a  vessel  provided  for  the  purpose.  Sometimes 
heat  is  necessary  in  order  to  make  the  reaction  take  place. 
Sometimes  both  compounds  remain  in  solution.  The  equations 
are  as  follows : 

Cu  (copper)  +  O  =  Cu  O  (cupric  oxide). 

C+  O2  =  CO2  (carbonic  di-oxide). 

Cu  +  H2  SO4  (sulphuric  acid)  =  Cu  04  (cupric  sulphate)  +  2H. 

Zh  +  H2  SO4  =  Zn  SO4  (zinc  sulphate)  +  «H. 

Fe  +  H2  SO4  =  Fe  SO4  (ferric  sulphate)  -f  zH. 

2  Na  (sodium)  +  2  (KaO)  =  z(Na  HO)  (sodic  hydrate)  +  aH. 


72 

2  K  (potassium)  +  2(H2O)  =  2(KHO)  +  2H. 
Fe3  _j_  4  H2O  =  Fes  °4  (ferric  oxide)  +  8H. 
Cu  O  (cupric  oxide)  +  2H  =  Cu  +  H2O. 
NaaO  (sodic  oxide)  +  H2O  =  2(Na  HO)  (sodic  hydrate). 

Ca  O  (calcic  oxide)  +  H2O  (water)  =  Ca  (HO)2  (calcic 
hydrate). 

P20S  +  3  (H20)  =  2(H3  P04). 

2  (HC1)  (hydrochloric  acid)  +  Ba  H2  63  (baric  hydrate)  =  Ba 
Cb  (baric  chloride)  +  H2  O2  (peroxide  of  water)  + 
H2O  (water). 

Ag2  SO4  (argentic  sulphate)  -f-  Ba  C12  =  2  Ag  Cl  (argentic 
cloride)  +  Ba  SO4  (baric  sulphate). 

Ba  C12  (baric  chloride)  +  H2  864  (sulphuric  acid)  +  Ba  SO4 
(baric  sulphate)  +  2(HC1)  (hydrochloric  acid), 

Ha  O  +  C12  =  C1  HO  (chloric  acid)  +  HC1  (hydrochloric  acid) 
NH4  (NO2)  (ammonia  nitrate  +  slight  heat  =  N2  + 
2  H20). 

KNO2  (potassic  nitrite)  +  NH4  Cl  (ammonic  chloride)  +  H2O 
=KC1  +  NO2  NH4  (ammonic  nitrate)  +  H2O. 

H2  SO4+  KNO3  =  HKSO4  (double  sulphate  of  potassium  and 
hydrogen)  +  HNO3  (hydric  nitrate,  commonly  called  nitric 
acid). 

Cu3  +  8(HNO3  =  3(Cu  (NOs)2)  (cupric  nitrate)  +  2(NO) 
(nitric  oxide). 

HNOs  +  KHO  =  KNO3  +  H2O. 

Pb  (NO3)2  (plumbic  nitrate)  +  heat  =  PbO  (plumbic  oxide)  + 
N2O4  (nitric  peroxide)  +  O. 

NO  (nitric  oxide)  +  $H  +  heat  =  NH3  (ammonia)  +  H2O. 


73 

Hz  SO4  (hydric  sulphate,  called  also  sulphuric  acid)  +  2KNO* 
=  K2  S04  + 


2  (NH4  Cl)  (ammonic  chloride)  +  Ca  H2O  (calcic  hydrate) 
=  2NH3  +  Ca  C12  +  2  (H2O). 

(NH4)  HO  (ammonic  hydrate)  +  HNO3  =  (NH4)  NO3  +  H2O. 
KHO  =  KNO3  +  H2Q. 


Pb      (N03)2  +  2  (NH4)HO)  =  2(  (NH4)N03)      (ammonic 
nitrate)  +  Pb  (HO)  2. 

HNa  CO3    (double    carbonate   of   sodium   and   hydrogen)  + 
H2SO4  =  H  Na  SO4  -f  H2O  +  CO2. 

CH4  (carburetted  hydrogen  or  carbonic  hydride)  +  aO2  +  heat 
=  CO2  +  2H2O. 

Mn  O2  (manganic  oxide)  +  4(HC1)  +  heat  =  Mn  Cl2  +  Cl2  + 
2  H2O. 

Cl2  +  2  (KHO)  =  KC1  +  KC1  O  +  HzO. 

Ba  (Cl  O3)2  (baric   chlorate)  +  H2SO4  =  2(HC1  O3)  (hydric 
chlorate)  +  Ba  804. 

Cl2  +  H2O  +  AgNO3  (argentic  nitrate)  =  Ag  Cl  +  HC1  0  + 
HN03. 

HC1  +  HC1  O  =  Cl2  +  H2O. 
H2SO4  +  Na  Cl  =  Na  HSO4  +  HC1. 
Na  HSO4  +  Na  Cl  =  Na2SO4  +  HC1. 
KHO  +  HC1  =  KC1  +  H2O. 

Hg2    (NO3)2  +  2(HC1)  =  2Hg  Cl  (mercuric    chloride)  + 
2(HN03). 

(NH4)2  CO3  +  Ca  Cl2  =  2(NH4  Cl)  +  Ca  CO3. 


74 
CA  S04  +  Ba  2(N03)  =  Ca  2  (NO3)  +  Ba  SO4. 

2  (Ag  NO3)  +  Ca  Cl2  =  2  (Ag  Cl)  (argentic  chloride)  +  Ca 
(N03)2. 

Pb  (NO3)2  +  H2  S  (hydric  sulphide)  =  2  (HNO3)  +  Pb  S. 
2  (HN03)  +  Ba  H2O  =  Ba  (NO3)2  +  2  (HzO). 

2  (As  C13)   (arsenic  chloride)  +  3  (H2S)  —  6  HC1  +  As2  S3 
(arsenic  sulphide). 

Bi  C13  (bismuth  chloride)  +  3  KI  (potassic  iodide)  =  Bi  I3  + 
3  (KC1). 

2  HC1  +  Pb  (NO3)2  =  2  (HNO3)  +  Pb  Cb. 

Se  O2  (selenious  acid)  +  H2S   (hydric  sulphide)  —  Se  82  +  2 
(H2O). 

Ba  Se  O4  (baric   seleniate)  +  4  HC1  =  Se  O2  +  Ba  Cl2  +  2 

(H2O)   +  Cl2. 

Te  O2  (tellurous  acid)  +  2  H2S  =  Te  82  +  2  (H2Q). 

Pb  (NO3)2  +  2  (Na  HO)  (sodic  hydrate)  =  Pb  (HO)2  +  2  Na 
N03. 

Pb  (NO3)2  +  H2  S04  =  H2  (NO3)2  +  Pb  SO4. 
PC13  +  3  H20  =  P  (H0)3  +  3  HC1. 
BC13  (boric  chloride)  -f  3  (H20)  =  B  (HO)3  +  3  (HC1). 
Cu  SO4  +  2  (KHO)  =  Cu  (HO)2  +  K2  SO4. 

3  (Si  F4)  (silicic  fluoride)  +  2  (H2O)  •-  2  (H2  Si  F6)  +  SiO2. 

Mn  SO4  (manganic  sulphate)  +  2  Na  HO)  =  Mn  (HO)2  (man- 
ganic hydrate)  +  Na2  SO4. 

Sb2  (antimony)   +  6   (H2  SO4)  =  Sb2  (SO4)  3  -(-  6  H2O  +  3 

(SO2). 


75 

Zn  SO4  +  2  (KHO)  =  Zn  (HO)*  +  K2  804. 
Sb2  83  +  Fes  =  Sba  +  3  (Fe  S). 
Sb2  83  +  6  (HC1  )  =  2  (Sb  Cl  )3)  +  3  (H2S). 
Co  (NO3)2  +  2  (Na  HO)  =  Co  (HO)2  (cobaltic  hydrate)  +  2 

Mn  SO4  +  (NH4)2  Co3  (ammonic  carbonate)  =  Mn  CO}  + 
(NH4)  2  S04. 

2  HC1  +  Sn  =  Sn  Cb  (stannous  chloride)  +  H2. 

3  Fe  SO4  +  Au  Cl3  (auric  chloride)  =  Fe  Cl3  -f  Fe3  (804) 

3  +  Au. 

Ba  (N03)2  +  (NH4)2  CO3  =  Ba  CO3  +  2  (NH4)  (NO3) 
(ammonic  nitrate). 

HNa2  PO4  (hydro  di-sodic  phosphate)  +  3  (Ag  NO3)  =  Ag3 
PO4  (argentic  phosphate)  +  2  Na  NO3  (sodic  nitrate)  +  H 
N03). 

Hg2O  (mercuric  oxide)  +  2  HC1  =  2  (Hg  Cl)  +  H2O. 

2  H  (CN)  (hydric  cyanide)  +  2  (Hg  (NOs)2  =  (mercuric  cyan- 
ide) 2  Hg  +  2  H  (N03). 

Ca  SO4  +  (NH4)2  CO3  =  Ca  SO4  +  (NH4)2  (SO4). 
Hg  SO4  +  Hg  +  2  Na  Cl  =  2  (Hg  Cl)  +  Na2  804. 
Sr  (NO3)2  +  Ca  SO4  =  Sr  SO4  +  Ca  (NO3)2. 

Al  SO4  -f  2  (NH4)  (HO)  -  Al  (HO2)  +  (NH4)  2SO4  (am- 
monic sulphate). 

HC1  +  Ag  N03  =  HN03  +  Ag  Cl. 

H2S  +  2  (Hg  NO3)  (mercurous  nitrate)  =  Hg2  S  +  2  (H 
(N03)-) 


H2S  +  Pb  (NO3)2  =  2  (H  (NOs)  )  +  Pb  S. 


76 

HC1  +  Hg  (NOs)  =  H  NO3)  +  Hg  Cl  (mercurous  chloride). 
2  (Na  Cl)  +  Hg  S04  =  Hg  Cl2  +  Na2  SO4. 

Hg  Cb  +  2  (NH3)  =  Hg  NH2  (double  chloride  of    mercury 
and  hydrogen)  -f  (NH4>  Cl. 

2  KI  +  Pb  (NOs)2  =  2  KNC-3  -f  Pb  12. 

2  (Na  Cl)  +  Hg  SC-4  =  Hg  Cb  +  Na2  804. 

2  Sn  Cl  (stannous  chloride)  +  H2  S=  Sn  S  +  2  (HC1). 

Sn  Cb  (stannic  chloride)  +  H2S  =  Sn  S  +  2  (HC1). 

Sn  Cb  +  2  KHO  =  Sn  (HO)2  +  2  (KC1.) 

Hg  Cl2  +  Cu  =  Hg  +  Cu  Cl2. 

2  Ag  NC-3  +  H2SC-4   =  Ag2  SO4  -f  2  HNOs. 

Ag  N03  +  (NH4)  (HO)  =  Ag  HO  +  NH4  NO3. 

Sr  Cl2  +  Ca  SO4  =  Sr  SO4  +  Ca  Cl2. 

Ba  Clz  +  2  Na  HO  —  Ba  (HO)2  +  2  (Na  Cl). 

Ca  Cl2  +  (NH4)2  CO3  Ca  CO3  +  (NH4)2  COs. 

Al  Cl2  +  2  (NH4)  HO  =  Al  (HO)  2  +  2  (NH4)  Cl. 

Cu  SO4  +  2  KI  =  Cu  I  +  K2  SO4. 

Hg  Cl2  +  2  KI  =Hg  12  +  2  KC1. 

Cu  SO4  +  H2S  =  Cu  S  +  Ha  SO4. 

Au  C13  +  3  KI  =  Au  I3  +  3  KC1. 

Pt  C14  +  4  KI  =  Pt  I4  +  4  KC1. 

Hg  Cl2  +  H2S  =  Hg  S  +  2  HC1. 

2  Au  Cl3  -f  3  H2S  =  Au2  83  +  6  HC1. 


77 

Sn  Cl2  (stannic  chloride)  +  H2S  =  Sn  S  +  2  HC1. 
Sb2  S3  +  6  HC1  =  2  Sb  C13  +  3  H2S. 
2  HC1  +  Sn  =  Sn  Cla  +  H2. 
(Ag  N03)  +  Cl  Na  =  Cl  Ag  +  NO3  Na. 
PO4  Na  H  +  3  Ag  NO3  =  PO4  Ag3  +  2  Na  PO4  +HNO3. 
Hg2  O  =-  Hg  +  Hg  O. 
Hg2-  O  +  2  HC1  =  Hg2  Cl2  +  H2O. 

Hg  (N03)2  (H2O)3  +  nH2O  =  Hg2  NO3HO  +  NO3H  + 
(n  +  a)  H2O. 

2  H  (CN)  +  Hg2  (NO3)2  =  Hg  (CN)2  +  Hg  +  2  HNO3. 
Hg2  (NO3)2  +  2  Na  Cl  =  Hg2  Cl2  +  2  Na  NO3. 

2  Hg  (NO3)  +  H2SO4  +  2  Na  Cl  +  H2O  =  Hg  2  Cla  + 

Na2  SO4  +  4  HNO3. 

3  Ab  O3  +  3  Si  F4  =  Al2  O3  (Si  O2)3  +  2  A12  F6. 
5  Si  O2  +  2  Ala  F6  =  2  (Ala  O3  Si  02)  +  3  Si  F4. 
3  Si  F4  +  2  H2O  =  2  H2  Si  F6  +  Si  O2. 

2  HSi  FS  +  2  KHO  =  2  K  Si  FS  +  2  H2O. 

2  HSi  FS  +  6  KHO  =  6  KF  +  4  HaO  +  Si  Oa. 

3  Ca  F2  +  B2Q3  -  3  Ca  O  +  2  BF3. 
2  BF3  +  3  H2O  =  B2  O3H6F6. 

4  (B2O3H6F6)  =  B2O3  +  9  H2O  +  6  (HBF4). 
Fe  S  +  H2SO4  =  H2S  +  Fe  SO4. 


78 

Sb2  83  +  6  HC1  =  3  H2S  +  2  Sb  03. 
HaS  +  03  =  H20  +  802. 
N2Os  +  6  H2S  =  2  NH3  +  3  H2O  +  S6. 
Sn  +  H2S  =  H2  -f  Sn  S. 

2  Fe  S  +  03  =  Fe2  03  +  82. 

3  Ca  O  +  S6  =  Ca  8203  +  3  Ca  82. 
Ca  82  +  2  HC1  =  Ca  Cb  +  H2S  +  S. 

2  (Fe  S04)  +  O  =  Fe  03  (SO3)2. 

Fe  82  +  H2  O  +  Oy  =  Fe  SO4  +  H2  SO4. 

3  SO2  +  H2  (NO3)2  +  2  H2O  =  3  (H2SO4)  +  2 
NO2  +  SO2  +  H2O  =  NO  +  H2SO4- 

2  NO2  +  2  SOz  +  H2O  =  2  (NSO4)  H2Q. 

2  (NSO4)  H2O  +  H2O  =  2  NO  +  2  (H2SO4). 

3  SO2  +  H2(NO3)2  +  2  H2O  =  2  NO  +  3  (H2SO4). 
2  SO2  +  2  NO2  +  2  H2O  =  2  (H2SO4)  +  2  NO. 

2  Ag  +  2  (H2SO4)  =  Ag2  SO4  +  2  H2O  +  SO2. 

Mn  O2  +  H2SO4  =  Mn  SO4  +  O  +  HzO. 

2  Cr  03  +  3  (H2S04)  =  Cr2  O3  (SO3)3  +  O3  +  3  H2Q. 

2  (Fe  804)  +  heat  =  Fe2  O3  +  SOz  +  803. 

K.2  804  +  €4  =  K2S  +  4  CO. 

2  Ca  S  +  04  =  Ca  S2O3  +  Ca  O. 

Ca  8203  +  Na2  CO3  =  Ca  CO3  +  Na2  8203. 


79 

2  Ag  Cl  +  Na2  8203  =  2  Na  Cl  +  Ag2  8203. 

3  SO2  +  Zn2  =  Zn  OSO2  +  Zn  S2O3  +  ZO3. 

4  (Na2  8203  5  H2O)  =  20  H2O  +  3  (Na2  SO4)  +  Na2  85. 

3  (K2O)   (H20)  (S02)2  +  8=2  (K2S3O6)  +  K2OSO2    + 
3  H2O. 

V 
H2S3O6  =  H2SO4   +  SOa  -f  8. 

Fe2  C16  +  2  (Na2  8203)  =  Na2  S4O6  +  2  Fe  C12  +  2  NaCl. 

5  HzS  +  5  SO2  =  H2SsO6  +  4  H2O  +  85. 
2  CS2  +  2  H2S  +  Cu6  =  6  Cu  8  +  C2  H4. 
CS2  +  2  NH3  =  H2S  +  NH3  HCNS. 
K2CS3  +  2  HC1  =  H2CS3  +  2  KC1. 
K2CS3  +  3  H2O  =  K2CO3  +  3  H2S. 

2  S2Cl2  +  2  H2O  =  4  HC1  +  802  +  83. 
H2SO3  +  H2O  +  2  SO2  =  2  (H2SO4)  +  8. 
Pb  8204  +  H2S  =  H2S2O4  +  PbS. 

2  HP03  +  C6  =  6  CO  +  H2  +  P2. 

3  Ca  (P03)2  +  2  (H2S04)  =  Ca  (H2  (PO3)2)2  +  2  (Ca  SO4). 
3  Ca  (P03)2  +  Cio  =  3  Ca  (PO3)2  +  10  CO+  P4. 

3  Ca  (P03)2  +  6  HC1  +  C8  =  3  Ca  Cl2  +  8  CO  +  H6  +  P2. 

3  H2  (P03)2  +  3  (Ag2  (N03)2  +  3  NH3  =  3  Ag2  (PO3)2 
3  NH3H2 


2  Na2  OH2  (P03)2  +  3  (Ag2  (NO3)2)  =  3  Ag2  (PO3)2  +  2 
(Na2  (N03)2)  +  H2  (N03)2. 


80 


2  Na2  (PO3)2  +  2  (Ag2  (NO3)2)   =  2  Ag2  (PO3)2  +  2  (Na2 
(N03)2). 

(Na  0)2  (NH4)2  H2  (PO3)2  +  3  (Ag  (NO3)2)  =  Na2  (NO3)2 
+  (NH4)2  (N03)2  +  H2  (N03)2. 


Na2  (PO3)2  +  Ag2  (N03)2  =  Ag2  (PO3)2  +  Na2 

3  (Cu  SO4)  +  2  PH3  =  3  (H2SO4)  +  P2Cu3. 

PCls  +  H20  =  PC13  0  +  2  HC1. 

3  PCls  +  3  H2B2O4  =  3  PC13  O  +  6  HC1  +  B2Q3. 

PCls  +  HaS  =  PC13  S  +  2  HC1. 

2  PC3S  +  6  Na2  O  =  6  Na  Cl  +  3  Na2  P2O4S2. 

2  PC13  +  3  H2S  —  PzS3  +  6  HC1. 

2  NH3  +  P2Os  =  H2O  +  N2  (HO)4. 

PC13  O  +  3  NH3  =  3  HC1  +  N3H6PO. 

PC13  S  +  3  NH3  =  3  HC1  +  (NH3)2PS. 

PCls  +  2  NH3  =  2  HCl  +  N2H4PC13. 

N2H4PC13  +  H20  =  N2H3PO  +  3  HCl. 

N2H3PO  +  heat  =  NH3  +  NPO. 

As2  O3  +  C3  =  As2  +  3  CO. 

As2  O3  +  H2ON2O5  +  2  H2O  =  N2O3  +  3  H2OAs2  05. 

Zn3  As2  +  3  (H2SO4)  =  2  As  H3  +  3  (Zn  SO4). 

2  As  HS  +  O6  =  Asz  O3  +  3  H2O. 

As2  O3   +  Zn6  +  6  (H2SO4)    =   2  As  H3   +  6(Zn  SO4) 
3  H2O. 


81 

2  As2  03  +  87  =  2  As2  82  +  8  SOz. 

Fe  82  Fe  As  2  +  2  Fe  82  =  4  Fe  8  +  As2  82. 

3  As2  03  +  2  HC1  =  2  (As3  Cl  O4)  +  H2Q. 
89  +  2  As2  03  =  2  As2  83  +  8  SO2. 

2  Na2  H2OAs  O6  +  7  H2S  =  8  EbO  +  2  Na2  Asa    86. 
2  Na2  As2  86  +  4  HC1  =  4  Na  Cl  +  2  H2S  +  2  As2  85. 
Ca  CO3  +  2  NH4C1  =  Ca  C12  +  COs  (NH4)2. 
Heat  +  3  Ca  Cl2  O2  =  Ca  (Cl  O3)2  +  2  Ca  Cl2. 

2  Ca  S  +  2  H2O  =  Ca  O2  H2  +  Ca  O2H2  +  Ca  S2H2 

3  Ca  O2H2  +  6  82  =  2  Ca  85  +  Ca  8203  +  3  H2Q. 


2  PO4Mg  NH4  (H2O)6  +  heat  =  Mg2  P2O7  +  2  NHs  +  13 

H2O. 

HKO  +  K  =  K2O  +  H. 

K2CC-3  +  Ca  H2O2  =  2  KHO  +  Ca  CC«3. 

SO4K2  +  Ba  (HO)a  ^SO4Ba  +  2  KHO. 

NOsNa  +  Cl  K  =  NO3K  +  Cl  Na. 

NH3  +  K  =  NH2K  +  H. 

Heat  +  3  NH2K  =  NK3  +  2  NH3 

(CN)6  Fe  K4  +  COsK2  =  5  KCN  +  CNKO  +  Fe  +  CO2. 

KOCN  +  2  H2O  =  COsHK  +  NH3. 

Heat  +  3  KC1  O  =  2  KC1  +  Cl  O3K. 

(Cl  O3)2  Ca  +  2  KC1  =  2  KC1  O3  +  Cla  Ca. 

3  Br2  +  6  KHO  =  5  KBr  +  KBr  O3  -f  3  H2O. 


82 

S2K2  +  2  HC1  =  SH2  +  2  KC1  +  S. 
SO4K2  +  HC1  =  S04KH  +  Cl  K. 
SO4H2  +  Cl  Na  =  SC>4Na  H  +  HC1. 
Na  HS04  +  Na  Cl  =  SO4Na2  +  HC1. 
Heat  +  2  SO4NaH=  8207^2  +  H2O. 
Na2  HPO4  +  NO3H  =  NO3Na  +  PO4Na  H2. 
Na2  HPO4  +  HONa  =  PO4Na3  +  H2O. 
Na2  HPO4  +  Cl  NH4  =  PO4Na  (NH4)  H  +  Cl  Na. 
Ca  COs  +  2  HC1  =  Ca  C12  +  H2Q  +  CO2. 
4  H2O  +  C3  =  C02  +  2  CO  +  H8. 
Sis  H4Os  +  12  KHO  =  3(2  K2Si  O2)  +  H6  +  5  H2O. 
2  (NH3HC1)  +  Ca  O  =  Ca  C12  +  H2Q  +  2  NH3. 

2  NH3  +  CaO  +  O8  =  Ca  ON2Os  +  3  H2O. 
KNO3  +  H2SO4  =  HNO3  +  KHSO4. 

4  (H2(N03)2)  +  Cu3  =  3  (Cu(N03)2)  +  2  NO  +  4  H2Q. 

3  N2O3+  H2O  =  H2  (NO3)2  +4  NO. 
2  NH3  +  N203  =  N4  +  3  H2O. 

2  (NH3HC1)  +  K2ON2O3  =  N4  +  2  KC1  +  4  H2Q. 
H2  (NO3)2  -f  As2  O3  =  H2OAS2  O6  +  N2O3. 

3  NO2  +  H2O  =  NO  +  2  HNO3. 
NO  +  2  (HN03)  =  3  N02  +  H20. 

2  N2Q2  +  4  (KHO)  =  2  K  +  K2  (NO3)2  +  2  H2Q. 


83 

2  H2  (NO3)2  4-  Sn  =  2  H2O  +  4  NO2  +  Sn  O2. 

3  (H2  (N03)2)  +  Ag4  =  3  H20  +  N2Q3  +  2  (Ag2  (NO3)2). 

4  (H2  (NO3)2)  +  Cu3  =  4  H20  +  2  NO  +  3  (Cu  (NO3)2). 

5  (H2  (NO3)2)  4-  Zn4  =  5  H2Q  +  N2Q  +  4  (Zn  ON2Os). 

2  Na  Cl  4-  Mn  O2  4-  2  (H2SO4)  =  Na2  SO4  +  Mn  SO4  +  2 
H2O  4-  Cl2. 

Mn  O2  4-  4  HC1  =  Mn  Cb  +  2  H2O  +  C12. 

4  (Ca  (HO)2)  +  C14  =  (Ca  OCb  O  +  Ca  Ch  +  2  CaO)  +  4 
H2Q. 

(Ca  OCbO  +  Ca  C12)  +  2  (H2SO4)  =  2  (Ca  SO4)  +  2  H2O 

+  C14. 


2  Na  Cl  +  H2OSO3  =  2  HC1  +  Na2 

Fe  +  2  HC1  =  Fe  Cb  +  H2. 

Na  +  HC1  =  Na  Cl  +  H. 

Ag2  O  +  2  HC1  =  H2O  +  2  Ag  Cl. 

Cu2  O  +  2  HC1  =  H2O  +  Cu2  Cl2. 

Sb2  O3  +  6  HC1  =  3  H2O  +  2  Sb  C13. 

Mn2  O3  +  6  HC1  =  3  H2O  -f  2  Mn  Cb  +  Cla. 

Mn  O2  +  4  HC1  =  2  H2O  +  Mn  Cb  +  Cb. 

Hg  O  +  C14  =  Hg  Cb  +  CbO. 

Cb  O  +  2  HC1  =  H2O  +  C14. 

HN03  4-  3  HC1  =  2  H2O  +  NOCla  4-CL 

NOCb  4-  H2O  =  2  HC1  +  NQ2. 

6  KHO  +  Br6  =  5  KBr  +  KBr  O3  +  3  H2Q. 


84 

2  KBr  +  Mn  02  +  2  (H2SO4)  =K2SO4  +  Mn  SO4  +  2  Hz 
O  +  Br2. 

6  H2O  +  Br6  +  Pa  =  3  H2PO4  +  6  HBr. 

2  Na  I  +  Mn  O2  +  2  (H2SO4)  =  Na2  SO4  +  Mn  SO4  +  2 
H2O  +  12. 

6  KHO  +  16  =  5  KI  +  KIO3  +  3  H2O. 

5  KI  +  KIO3  +  6  HC1  =  6  KC1  +  3  H2Q  +  16. 

Na2  (103)2  +  2  Na2  O  +  C14  =  Na2  (104)2  +  4  Na  Cl. 

2  Na2  (104)2  +  4  (Ag  NO3)  =  2  Ag2  (104)2  +  4  (Na  NO3). 


2  Ag  (104)2  +  H2  (NO3)2  =  Ag2  OI207  +  Ag2 
H2O. 

2  (Ag2  (104)2)  +  H2O  =  O;  2  Ag2  (104)2  +  H2IO8O7. 
8  H2O  +  Iio  +  P2    =  10  HI  +  3  H2  (P03)2. 
4  KI  +  3  H2  (PO3)2  =  4  HI  +  2  K2H2  (PO3)2. 
NHI2  =  N  +  HI  +  I. 

Fe  I2  +  Fe2   16  +  4  (K2CO3)   =   8  KI  +  Fe  OFe2  O3  +  4 
CO2. 

Ca  F2  +  H2SO4  =  Ca  SO4  +  2  HF. 

2  Ca  F2  +  Si  O2  +  2  (H2OSO3)  =  2  (Ca  OSO3)  +  SI4  +  2 
H2O. 

Si  F4  +  2  H2O  =  Si  O2  +  4  HF. 

Hg  SO4  +  Hg  +  2  Na  Cl  =  Hg2  Clz  +  SO4Naa. 

Hg2  C12  +  2  NH3  =  Hg2  Cl  NH2  +  NH4  Cl. 

2  Na  Cl  +  Hg  SO4  =  C12  Hg  +  SO4  Na2. 

Hg  Cl2  +  2  NH3  =  Hg  NH2C1  +  NH4C1. 


85 

Hg  Cl2  +  Cu  =  Hg  +  Cu  Cb. 
3  Hg  SO4  +  2  H20  =  Hg3  SO6  +  2  H2  SO4. 
PbS  +  3O  =  PbO  +  SO2. 
Pb  S  +  2  O2  =  Pb  SO4. 

Pb3  O4  +  4  HNO3  =  2  Pb  (NO3)2  +  Pb  Oz  +  2  H2O. 
Pb  O2  +  4  HC1  =  Pb  Cl2  +  Cl2  +  2  H2O. 
3  Bi  Cls  +  4  H2O  =  Bi3  O2C13  (HO)a  +  6  HCL 
2  Cu  O  +  Cuz  S  =  2  Cu2  +  SO2. 
Fe  +  SO4  Cu  =  SO4  Fe  +  Cu. 
Cu2  H2  +  2  HC1  =  Cu2  Cb  +  2  H2. 
2  Cu  SO4  +  4  KI  =  Cu2  12  +  12  +  2  K2SO4. 

2  HNa2  PO4  +  3  Cu  SO4  =  Cu3  (PO4)2  +  2  Na2  SO4  + 
H202  SO4. 

C  +  C02  =  2  C02. 
C  +  H20  =  CO  +  H2. 

2  Fe2  H6O6  —  3  H2O  =  Fe4  OpHd. 

3  Ba  CO3  +  Fe2  C16  =  3  CQ2  +  Fe2  O3  +  3  Ba  Cb. 

Fey  Cyi8  +  12  KHO  =  3  Fe  Cy6  K4  +  2  Fe2  O3  +  6  H2Q. 
Fe2  Cyi2  +  3  Fe  Cls  =  Fes  Cyi2  +  6  KC1. 

Fes    Cyi2    +    8    KHO    —   2    Fe   Cy6   K4   +  Fe2  H6O6  + 
Fe 


Fe2  C16  +  6  KI  =  2  Fe  12  +  I2  +  6  KC1. 
Fe  S  +  2  HC1  =  Fe  CI2  +  H2S. 


86 

Fe2  C16  +  H2S  =  2  Fe  Ch  +  2  HC1  +  S. 
2  Fe  S04  =  SO2  +  Fe2  O2SO4. 
Ab  O3  +  3  C  +  3  Cl2  =  Al2  C16  +  3  CO.  0 

Ab  C16  +  (  (NH4)2  8)3  +  6  H2O=  Ala  O6H6  +  3  H2S  + 
6  NH4C1. 

Cr  (SO4)s  +  3  (NH4)2S  +  6  H2O  =  Cr2  H6O6  +  3  (NH4)2 
SO4  +  3  H2S. 

2  Cr  03  +  12  HC1  =  Cr2  C16  +  6  Cl  +  6  H2Q.       , 

2  Cr  03  +  6  HC1  +  3  H2S  =  Cr2  C16  +  3  S  '+  6  H2O. 

Cr  O4K2  +  2  Na  Cl  +  2  H2<D4Cr  O2C12  +  SO4K2  +  SO4Naz 
+  2  H2O. 

2  Cr  03  +  3  H2SO4  =  Cr2  (SO4)3  +  3  O  +  3  H2O. 

K2Cr2  O7  +  12  NH4F  +  7  H2SO4  =  2  Cr  F6  +  K2SO4  + 
6  (NH4)2SO4  +  V  H2O. 

C02C16  +  3  Ba  CO3  =  Co2  03  +  8  COa  +  3  Ba  Cb. 
Mn  S  +  Co  Cl2  =  Mn  Cl2  +  Co  S. 

3  K2Mn  O4  +  2  H2Q  =  K2Mn2  O8  +  Mn  O2  +  4  KHO 
Ba  S  +  2  HNO3  =  (NO3)2Ba  +  H2S. 

SO4Ba  +  2  C2  =  SBa  +  4  CO. 

6  Ba  H2O2  +  6  I2  =  Ba  (103)2  +  5  Ba  la  +  6  H2O. 

Miscellaneous  principles  and  facts  are  as  follows  : — 

Quick-lime,  phosphoric  anhydride,  and  sulphuric  acid  (con- 
centrated) absorb  with  avidity  moisture  from  the  air. 

Hydrogen  is  the  lighest  substance  known,  being  a  rare  gas; 
while  platinum  is  the  heaviest,  except  one  or  two  rare  metals. 

Sodium  and  potassium,  and  not  aluminium,  are  the  lightest 
metals,  being  light  enough  to  float  upon  water. 


87 

Hydrogen  gas  has  not  been  liquefied  by  pressure,  but  car- 
bonic acid  gas  and  ammonia  gas  have  been,  and  can  be  without 
difficulty,  with  the  proper  apparatus.  Hydrogen  gas  has  the 
property  of  passing  through  hot,  but  not  cold,  iron,  palladium, 
and  platinum.  Hydrogen  is  combustible  with  oxygen,  chlorine, 
and  a  few  other  elements  by  the  action  of  heat ;  or,  indirectly, 
by  placing  certain  compounds  in  contact  with  one  another. 
Hydrogen  and  chlorine,  when  mixed  and  exposed  to  sunlight, 
explode  violently  with  formation  of  hydrochloric  acid.  Colored 
textile  materials  are  bleached  by  the  action  of  chlorine  or  by 
ozone ;  because  these  two  elements  have  a  strong  affinity  for 
hydrogen,  and  because  all  aniline  and  vegetable  colors  are  due 
to  the  presence  of  hydrogen.  Chlorine,  when  absorbed  by 
water,  and  placed  in  the  sun,  will  decompose  a  portion  of  the 
water  uniting  with  the  hydrogen  and  liberating  the  oxygen.  If 
hydrogen  and  iodine  are  passed  over  platinum,  heated  to  red- 
ness, they  combine,  forming  hydriodic  acid;  whereas  water  is 
decomposed  into  hydrogen  and  oxygen  gases,  if  passed  through 
red-hot  iron  tubes.  About  the  only  chemical  which  acts  upon 
glass  is  hydrofluoric  acid,  and  the  action  is  so  great  that  in  a 
few  minutes  a  surface  of  polished  glass  looks  like  ground  glass. 
Although  all  water,  in  nature,  is  composed  of  oxygen  and  hydro- 
gen, it  also  contains  free  oxygen  absorbed,  which  may  be 
expelled  by  heat,  or  a  vacuum  pump,  or  absorption  by  some 
chemical  with  which  it  has  a  strong  affinity. 

The  temperature  of  a  flame  remains  at  that  at  which  com- 
bustion occurs,  so  that  a  very  slight  lowering  of  the  temperature 
will  extinguish  it;  therefore  a  piece  of  metal  gauze,  put  through 
a  gas  flame,  will  prevent  the  flame  from  coming  through  the 
gauze,  the  gauze  being  made  of  any  metal. 

At  the  ordinary  temperature,  phosphorus  will  unite  gradually 
with  oxygen,  becoming  white;  and  if  rubbed,  will  burst  into  a 
flame,  and  be  converted  into  a  cloud  of  white  fumes  of  the 
oxide  of  phosphorus;  and  similarly  all  metals  can  be  made  to 
combine  with  oxygen,  upon  rendition  that  the  temperature  is 
sufficiently  high. 

One-thousandth  of  a  pound  of  coal  gas,  when  exploded  with 
the  proper  proportion  of  air,  is  equivalent  to  a  force  which  will 
raise  a  weight  of  48  pounds  through  the  space  of  one  foot, 
showing  that  the  explosion  of  coal  gas,  by  an  electric  spark,  for 
instance,  produces  great  power. 

Water,  although  apparently  incompressible,  is  compressible 
to  the  extent  that  were  the  atmospheric  pressure  of  15  pounds 
to  the  square  inch  doubled,  1,000,000  volumes  would  become 
less  by  50  volumes.  It  is  a  very  bad  conductor  of  heat  and  of 


electricity;  and  is  not  known  to  conduct  the  latter  unless  by  it 
decomposed  more  of  less  into  hydrogen  and  oxygen  gases.  Above 
4°  C.  it  expands  by  heat,  and  it  is  a  remarkable  fact  that  below 
that  temperature  it  also  expands,  but  it  always  resumes  the 
same  density  at  any  given  pressure  and  temperature. 

Certain  solids  are  not  only  soluble  in  water,  but  also  certain 
liquids,  as  alcohol,  ether  and  acetic  acid;  and  also  gases,  as 
ammonia  and  hydrochloric  acid  and  nitric  acids;  the  rate  and 
degree  of  solubility  depending  upon  the  nature  of  the  gas,  the 
temperature  of  the  water,  and  the  pressure  upon  the  surface  of 
the  water. 

An  atmosphere  or  ocean  of  air  surrounds  the  earth,  and 
varies  in  pressure  from  the  top  to  the  bottom,  being  greatest  at 
the  latter  limit,  and  equal  to  15  pounds  per  square  inch. 

The  atmosphere  contains  intimately  mixed  nitrogen  and 
oxygen,  principally,  and  traces  of  water  vapor  and  carbonic  acid 
gas. 

The  atmosphere  has  the  property  of  a  lens,  in  that  after  the 
sun  has  actually  "  set  "  it  may  still  be  seen,  because  the  air  re- 
fracts or  bends  the  rays  downward. 

Carbon  occurs  in  three  distinct  physical  states — as  animal 
or  vegetable  charcoal  or  coke ;  as  representing  one  state 
properly  called  charcoal;  as  graphite  and  as  diamond;  so  that 
when  any  one  is  burned,  in  presence  of  pure  oxygen,  car- 
bonic di-oxide  alone  is  formed. 

Rain-water,  when  passing  through  the  air,  absorbs  such 
impurities  as  carbonic  acid  gas,  gases  from  chemical  works, 
factories,  &c. 

In  addition  to  phosphorus  having  the  property  of  lighting 
at  the  ordinary  temperature,  especially  if  rubbed  slightly,  phos- 
phoretted  hydrogen,  in  escaping  from  a  tube,  will  ignite  im- 
mediately and  continue  to  burn  as  long  as  the  supply  lasts. 

Litmus  is  a  liquid  having  the  property  of  turning  red  when 
mixed  with  an  acid;  of  turning  blue  when  mixed  with  an  alkali; 
and  being  changed  from  neither  red  nor  blue  when  treated  with 
any  other  known  substance. 

The  combustion  of  magnesium  metal  in  air  produces  in- 
tensity of  light  equal  to  that  of  the  arc  lamp  or  "calcium" 
light,  the  product  being  the  infusible  oxide  of  magnesium,  called 
magnesia. 

Zinc  becomes  brittle  at  the  temperature  of  about  205°  F. 

Certain  chemical  elements  can  be  combined  or  separated  by 
the  force  of  heat,  electrolytic  action,  light,  or  by  contact  with 
other  elements  or  compounds,  or  by  the  combination  of  those 
forces. 


89 

Although  mercury  is  the  only  liquid  elemental  metal, 
viscous  or  soft  metallic  substances  may  be  obtained,  as  amal- 
gams, by  mixing  certain  other  metals  with  mercury. 

Sodium  has  such  a  strong  attraction  for  mercury  as  to  com- 
bine therewith,  to  form  an  amalgam,  with  a  brilliant  light  and 
hissing  sound. 

The  most  abundant  element  in  the  world,  except  oxygen,  is 
aluminium,  and  exists  in  combination  with  oxygen  as  an  oxide, 
together  occasionally  with  small  quantities  of  potassium,  iron, 
calcium  and  magnesium.  Aluminium  is  only  about  two  and 
one-half  times  as  heavy  as  water;  while  iron  is  eight  times  as 
heavy  as  water,  and  platinum  is  twenty-one  times  as  heavy  as 
water. 

Although  ordinary  iron  has  the  property  of  receiving  a  de- 
posit of  copper  when  immersed  in  a  solution  of  a  copper  salt,  yet 
it  loses  this  property  if  first  mometarily  dipped  in  strong  nitric 
acid  and  then  washed. 

Wrought  iron,  cast  iron  and  steel  differ  from  one  another 
according  to  the  amount  of  carbon  they  contain  ;  wrought  iron 
containing  the  least  and  cast  iron  the  most  ;  while  the  temper  of 
steel  depends  upon  the  degree  of  heat  from  which  it  is  suddenly 
cooled.  The  electric  conductivity  of  steel  increases  with  its 
temper. 

These  different  iron  mixtures  with  carbon  have  different 
electrical  and  heat  conductivities  and  powers  of  magnetic 
reception. 

Nickel,  like  iron,  is  more  easily  fusible  when  containing  a 
small  quantity  of  carbon,  and  will  also,  like  iron,  at  a  red  heat,, 
decompose  water  into  hydrogen  and  oxygen. 

*  Cotton,  linen  and  wood  are  rendered  practically  incom- 
bustible when  treated  (in  the  manner  of  starching)  with  tungs- 
tate  of  soda,  which  will  also  serve  as  a  mordant  in  dyeing. 

A  bar  of  pure  tin,  when  bent,  emits  a  peculiar,  soft,  crack- 
ling sound. 

When  gold  is  rolled  sufficiently  thin,  it  will  transmit  light, 
and  will  have  a  color  dependent  upon  the  thinness  of  the  foil. 

Gold-leaf,  which  is  green  by  transmitted  light,  becomes  ruby 
red  when  heated  to  316°  F. 

Platinum  has  such  a  power  of  concentrating  oxygen  on  its 
surface,  that  when  a  coil  thereof  is  heated  in  an  alcohol  flame, 
and  the  flame  extinguished,  the  red-hot  platinum  will  continue 
to  be  red  hot,  even  in  the  absence  of  the  flame.  The  platinum 
must  remain  over  the  wick. 

"Platinum  black"  absorbs  more  than  800  times  its  volume 
of  oxygen. 


90 

There  are  no  two  substances  having  exactly  the  same  de- 
gree of  hardness;  and  of  two  substances,  that  one  which  leaves 
a  mark  upon  the  other,  by  friction,  is  the  harder.  Among  the 
hardest  substances  are  diamond  and  steel,  and  among  the 
softest  solids  are  soapstone,  potassium,  graphite  and  lead. 

A  weak  solution  of  chloride  of  cobalt  is  pink.  A  con- 
centrated solution  is  blue.  Paper  saturated  therewith  is  light 
pink  and  turns  blue  when  heated. 

Sulphur,  at  the  ordinary  temperature,  is  hard,  like  a  stone. 
When  first  heated,  it  is  very  thin,  and  when  heated  higher  it  is 
viscous  or  very  thick.  At  a  still  higher  temperature,  the  fused 
sulphur  becomes  again  thin,  and  in  cooling,  the  same  change 
takes  place. 

If  oxygen  i  volume,  and  hydrogen  2  volumes,  are  mixed  in 
a  vessel  and  exploded — for  instance,  by  a  spark — water  vapor 
is  produced  which  has  a  volume  of  only  f  the  gases  when  not 
combined,  /.  e.,  the  volume  is  only  2.  If  i  volume  of  chlorine 
and  t  of  hydrogen  are  combined,  the  result  is  2  volumes.  In 
general,  the  volume  after  combination  is  2,  even  if  the  volume 
of  the  elements  before  chemically  combining,  as  in  N 2  03  (nitro- 
gen peroxide),  is  5. 


91 
CHAPTER   XIII. 

PRINCIPLES    IN    ELECTRICITY    AS    TOOLS    FOR    MAKING 
SCIENTIFIC   INVENTIONS. 


ELECTRICITY  is  a  form  of  force.  What  it  is  further  than  this 
no  one  knows,  any  more  than  one  knows  what  gravitation  is. 

Two  general  classes  of  electricity  are  generally  named 
static  and  dynamic,  often  called  galvanic.  Similarly,  we  could 
speak  about  gravitation.  The  words  explain  the  difference. 
Static  electricity  is  the  condition  where  a  charge  tends  to 
flow,  but  cannot  because  the  circuit  is  not  complete.  It  is 
electricity  at  rest.  If  a  weight  rests  upon  the  floor,  there  is 
static  gravitation.  The  weight  tends  to  move,  but  cannot. 
Make  a  hole  in  the  floor  and  it  moves.  The  floor  acts  as  a 
resistance.  So  with  static  electricity;  it  does  not  move  because 
there  is  too  great  a  resistance;  there  is  no  proper  conductor  upon 
which  it  can  move.  As  soon  as  a  conductor  is  provided,  the 
current  flows.  This  current  is  called  dynamic.  Static  electricity 
is  often  spoken  of  as  frictional;  but  dynamic  electricity 
may  also  be  frictional.  However,  for  the  inventor,  he  cares  not 
for  names,  and  therefore  each  principle  and  fact  will  be  stated 
by  the  words  which  convey  the  information  in  as  simple 
a  manner  as  possible.  Gravitation  will  not  travel  along  a 
wire  and  back  again  to  the  generating  point,  but  an  electric 
current  will,  and  the  wire  may  be  tapped  at  any  point  and  the 
electric  energy  converted  by  the  proper  means  into  mechanical, 
chemical,  magnetic  and  light  energy.  If  the  wire  is  completely 
broken,  the  generator  of  the  electricity  maintains  the  wires 
charged,  but  performs  no  work. 

Electricity  is  generated  in  the  following  different  ways  : 
By  friction  or  when  two  substances  are  rubbed  together;  com- 
pression of  substances  ;  variation  of  temperature  upon  tour- 
maline; fracture  of  substances;  solidification  of  a  substance  from 
a  state  of  fusion  or  gas;  chemical  action  in  a  primary  or  secondary 
battery;  combustion  of  carbon,  the  same  being  electrified  nega- 
tively, and  the  resulting  carbonic  acid,  negatively;  by  evapor- 
ation of  a  liquid.  Fog,  snow  and  rain  are  found  to  be 
charged.  The  clouds  are  most  always  electrically  charged. 
It  is  generated  by  the  relative  motion  of  electro  or  permanent 
magnets;  by  induction  from  any  other  neighboring  circuit;  by 
certain  animals  and  fish  ;  by  heat,  as  when  two  different  metals 
are  touched  together  in  a  flame;  and  by  friction  of  clouds, 
producing  lightning. 


Light  is  claimed  to  be  converted  into  electricity  by  coating 
opposite  sides  of  a  plate  of  glass  with  sheets  of  tin-foil  (bright 
on  one  side  and  dull  on  the  other)  and  exposing  the  dull  side  to 
the  direct  rays  of  the  sun  and  dipping  in  alcohol.  The  electro- 
motive force  or  pressure  is  about  .06  volt.  The  dull  side  of  one 
sheet  of  foil  should  face  a  bright  side  of  the  other  sheet.  The 
current  passes  through  a  wire  connecting  the  sheets  of  tin- 
foil. 

Coat  two  silver  plates  with  silver  salts  or  aniline  dyes,  and 
immerse  in  a  conducting  liquid,  and  it  is  found  that  a  small 
current  is  generated,  if  electrically  connected,  while  one  plate  is 
exposed  to  light  and  the  other  placed  in  the  dark. 

Slight  electric  currents  may  be  obtained  from  the  earth  by 
connecting  a  well-insulated  and  long-distance  telegraph  line  to 
ground  at  both  ends,  omitting  all  electric  generators.  A  delicate 
galvanometer  needle  is  deflected,  but  resumes  its  original 
position  when  the  line  is  interrupted.  The  amount  of  current 
depends  upon  the  condition  of  the  tides;  upon  the  relative 
temperatures  of  the  two  points  of  the  earth  at  which  the  line  is 
grounded;  and  upon  the  condition  of  the  sun's  spots.  The 
direction  of  the  current  is  easterly,  and  the  maximum  is  in  the 
direction  from  N.  W.  to  S.  E.  ;  but  this  rule  is  found  to  be 
general  and  not  without  exception. 

The  generation,  of  electricity  by  chemical  action  consists  in 
a  transferring  of  the  atoms  from  one  compound  or  element  to 
other  elements  or  compounds.  When  this  change  takes  place, 
an  electric  current  is  produced.  The  chemical  force  is  changed 
into  electrical  force.  This  current  may  then  be  changed  again 
into  chemical  force  by  passing  it  through  a  solution  of  any  given 
compound,  whose  atoms  either  separate  or  rearrange  them- 
selves into  other  compounds,  or  unite  with  the  atoms  of  one  or 
more  other  compounds.  These  are  principles,  but  no  one 
knows  whether  the  chemical  and  electrical  forces  are  one  and  the 
same  thing  disguised  to  human  eyes. 

Electrical  conductors  are  as  follows,  being  approximately  less 
and  less  in  the  order  named :  Metals,  pure  graphite,  acids,  aqueous 
solutions  of  acids,  salts  or  hydrates;  animals,  vegetables,  water, 
snow,  linen  and  cotton.  The  non-conductors  are  principally  : 
Metallic  oxides;  ice  at  the  lowest  possible  temperature;  caout- 
chouc, dry  gases  or  mixture  of  gases;  dried  paper;  silk,  precious 
stones;  glass,  wax,  sulphur,  resins,  amber  and  shellac;  alcohol, 
flour  of  sulphur  and  powdered  glass. 

Carbon  being  of  high  resistance,  its  mixture  with  a  non- 
conductor increases  the  resistance  of  the  former  and  lowers  that 
of  the  latter  as  far  as  the  final  result  is  concerned.  Similarly, 


93 

fine  metallic  particles  mixed  with  carbon  result  in  a  substance 
of  different  resistance  from  either;  in  general,  substances  of 
different  resistance  (or  conductivity)  may  be  obtained  of  any 
desired  degree  by  mixing  different  substances  in  the  same  or 
different  proportions.  The  result  will  always  be  a  resistance 
differing  from  that  of  either  constitutent.  An  illustration  of  the 
application  of  this  principle  is  found  in  the  invention  of  the 
present  cheap  commercial  reduction  of  aluminium  from  its 
cheap  oxide,  which  is  a  non-conductor,  but  mixed  with  carbon 
is  practically  a  conductor.  The  passage  of  a  heavy  current 
heats  the  same  to  such  a  high  a  temperature  that  the  oxygen 
leaves  the  aluminium  and  goes  to  the  carbon,  forming  carbonic 
acid  gas,  which  escapes,  leaving  the  aluminium  free. 

The  relative  conductivity  of  conductors  is  as  follows  :  Silver 
being  taken  as  the  best  and  represented  in  value  by  100.  Cop- 
per is  nearly  as  good  a  conductor,  being  represented  by  99-9; 
gold  by  80;  sodium,  37;  aluminium,  34;  zinc,  29;  cadmium,  24; 
brass,  22;  potassium,  21;  platinum,  18;  iron,  17;  tin,  13;  lead, 
8;  German  silver,  8;  antimony,  5;  mercury,  2;  bismuth,  i; 
graphite,  o. 

The  relative  conductivity  of  some  liquids  is  indicated  by 
calling  that  of  silver  100,000,000,000,000.  Cupric  nitrate  satur- 
ated solution  in  water  would  be  represented  by  8,900;  cupric 
sulphate,  saturated,  by  5,420;  sodic  chloride,  saturated,  by  31,- 
520;  zinc  sulphate,  saturated,  by  5,770;  sulphuric  acid,  diluted 
so  as  to  be  1.24  times  as  heavy  as  water,  by  132,750;  com- 
mercial nitric  acid,  by  88,680;  and  perfectly  pure  water,  as 
obtained  by  distillation,  by  7. 

Reference  has  been  made  to  the  action  of  light  on  the 
conductivity  of  selenium.  Its  conductivity  is  doubled  in  direct 
sunlight.  Even  gas  light  increases  its  conductivity. 

In  the  following  principles  relating  to  the  electro-chemical 
generator  and  decomposition  it  is  assumed  that  it  is  known  that  a 
device  for  carrying  the  above  principles  into  effect  consists  of 
a  vessel  containing  a  liquid  called  conveniently  the  electrolyte 
and  two  pieces  of  solid  material  dipping  therein,  called  the 
electrodes.  A  wire  joining  the  electrodes  and  including  or  not 
including  electric  lamps,  or  bells,  or  motors,  &c.,  is  called  a 
circuit. 

The  electrolyte  may  be  a  single  conducting  acid,  dilute  or 
concentrated;  or  an  aqueous  or  acid  solution  of  a  decomposable 
salt,  oxide  or  hydrate.  Usually,  it  cannot  be  a  vegetable  or 
animal  substance.  If  of  the  same  metal,  a  current  is  not  pro- 
duced theoretically;  but  in  practice,  it  is  impossible  to  get  two 
pieces  which  have  the  same  molecular  structure,  temperature, 


94 

chemical  constitution,  &c.,  so  that  a  very  slight  current  may 
often  be  detected.  Not  only  should  the  metals  be  different  in 
order  to  obtain  large  currents,  but  the  electromotive  force 
(pressure)  and  current  are  dependent  upon  the  particular  metals 
joined  in  the  same  cell.  If  zinc  and  carbon  are  used  as  the 
electrodes  in  dilute  sulphuric  acid,  for  instance,  there  is  moire 
electromotive  force  than  if  iron  is  used  in  the  place  of  zinc; 
again,  the  electromotive  force  is  still  less  with  lead.  In  the  place 
of  solid  conductors,  gases  or  even  liquids  may  be  employed,  or  the 
electrodes  may  be  provided  with  a  coating  of  a  salt,  oxide  or  similar 
decomposable  compound.  As  far  as  the  elements  are  concerned, 
the  electromotive  force  is  higher  and  higher  according  to  the 
distance  apart  of  any  two. of  the  following-named  elements: 
Oxygen,  sulphur,  nitrogen,  fluorine,  chlorine,  bromine,  iodine, 
phosphorus,  arsenicum,  chromium,  boron,  carbon,  antimony, 
silicon,  hydrogen,  gold,  platinum,  mercury,  silver,  copper, 
bismuth,  tin,  lead,  cobalt,  nickel,  iron,  zinc,  manganese, 
aluminium,  magnesium,  calcium,  barium,  lithium,  sodium, 
potassium.  Example:  If  one  electrode  is  oxygen  (made  for 
instance  by  using  carbon  which  is  exposed  to  air)  the  electro- 
motive force  is  much  greater  with  a  second  electrode  of  lead 
than  of  silver.  The  electromotive  force  is  the  least  with  elec- 
trodes made  of  elements  which  are  next  to  each  other  in  the 
above  list.  The  electromotive  force  is  greatest  between  the 
first  and  last,  namely,  oxygen  and  potassium.  In  the  above 
series  dilute  sulphuric  acid  is  the  electrolyte.  The  series  varies 
a  little  with  other  electrolytes. 

The  fact  that  the  electromotive  force  increases  under  certain 
conditions  is  not  necessarily  a  proof  that  more  energy  is  obtained 
from  certain  amounts  of  chemical  actions  in  a  cell  any  more 
than  that  a  locomotive  necessarily  does  more  work  in  going 
from  New  York  to  Philadelphia  in  two  hours  than  in  three. 
More  work  is  done  in  the  former  case  in  a  given  interval,  but 
not  more  total  work. 

The  principles  upon  which  a  cell  in  general  produces  a  cur- 
rent may  be  explained  thus:  The  structure  in  the  first  place  is 
a  conducting  and  decomposable  liquid  which  serves  as  an  elec- 
trolyte. The  liquid  if  not  decomposable  is  not  operative. 
Thus,  mercury  is  a  conducting  liquid,  but  does  not  serve  as  an 
electrolyte.  Again,  the  liquid  should  be  not  only  a  compound, 
but  a  conducting  compound.  Oil  is  a  compound,  but  no  elec- 
trolyte. It  is  not  a  conductor.  The  electrolyte  may  consist  of 
several  liquids. 

The  chemical  actions  which  occur  in  a  cell  take  place  at  the 
surfaces  and  often  within  the  mass  of  the  electrodes;  but  not  much 


95 

beyond  the  surfaces.  The  maximum  action  takes  place  on 
those  surfaces  nearest  together.  The  larger  the  amounts  of 
surface  exposed  to  the  action  of  the  electrolyte,  the  greater  the 
current,  but  the  electromotive  force  remains  constant,  which, 
however,  may  be  increased  by  connecting  two  or  more  cells  in 
series,  /".  e.,  by  connecting  electrically  the  negative  electrode  of 
one  cell  with  the  positive  of  the  next  cell,  and  so  on.  Illustra- 
tion: If  each  cell  contains  electrodes  of  carbon  and  zinc,  the  zinc 
of  one  cell  is  connected  to  the  carbon  of  the  next,  which  is  con- 
nected to  the  zinc  of  the  next,  and  so  on,  the  final  carbon  and 
zinc  being  the  terminals  of  the  battery,  which  if  connected  by  a 
conductor  instantly  allows  the  chemical  actions  to  take  place 
and  a  current  to  flow.  If  like  electrodes  are  joined  in  sets  a 
current  is  found  by  joining  the  sets.  The  electromotive  force  is 
not  increased,  but  the  current  is.  The  product  of  the  current 
by  the  electromotive  force  is  equal  to  the  amount  of  electrical 
energy,  just  the  same  that  the  product  of  the  height  of  a  col-umn 
of  falling  water  by  the  amount  of  water  which  falls  equals  the 
amount  of  work  which  the  falling  water  performs. 

Sometimes  cells  may  be  electrically  connected  in  a  closed 
circuit  without  giving  a  current  by  connecting  all  the  zincs  and 
all  the  carbons  into  one  set  or  closed  circuit.  Various  combi- 
nations of  the  above  elementary  methods  of  connecting  up  cells 
may  be  made.  Thus  some  cells  of  a  given  set  may  be  joined  in 
series  and  others  in  parallel,  and  still  others  in  opposition,  the 
resulting  current  being  due  to  the  nature  of  the  combination. 

The  current  produced  by  the  chemical  action  in  a  battery 
will  produce  chemical  action  in  another  battery,  but  only  on  the 
condition  that  the  energy  of  the  former  current  is  greater  than 
that  of  the  latter.  Illustration:  Let  the  terminals  of  a  sulphuric 
acid  battery  be  dipped  in  dilute  sulphuric  acid.  Hydrogen  and 
oxygen  are  given  off  at  the  respective'  terminals,  which  will 
escape  into  the  air  or  combine  with  the  electrodes  according  to 
their  chemical  nature.  If  the  terminals  are  platinum,  the  oxygen 
and  hydrogen  both  escape,  except  that  a  small  amount  at  the 
beginning  will  be  mechanically  absorbed  by  the  platinum.  If 
the  oxygen  and  hydrogen  unite  with  the  electrodes  in  such  a 
manner  as  to  form  insoluble  compounds  thereon,  as  will  be  the 
case  with  lead  terminals,  the  same  will  act  as  a  good  cell  itself 
after  the  said  battery  is  taken  away.  Similarly,  any  secondary 
conducting  terminals  and  any  conducting  decomposable  elec- 
trolyte form  more  or  less  of  a  secondary  cell  after  the  primary- 
charging  battery  is  removed  and  the  cell  closed  upon  itself. 

Some  cells  give  a  constant  current  and  some  give  a  weaker 
and  weaker  current  until  the  final  is  very  weak.  The  latter 


96 

generally  are  formed  with  one  electrolyte;  the  former  with  two, 
separated  in  such  a  manner  that  they  can  mix  only  very  slowly, 
as  may  be  done,  for  example,  by  means  of  a  porous  earthenware 
jar.  When  two  electrolytes  are  employed,  an  electrode  is  placed 
in  each.  The  reason  why  a  single  electrolyte  cell  forms  a 
decreasing  current  is  that  bubbles  of  gas  collect  upon  the  sur- 
faces of  the  electrodes.  As  gases  are  bad  conductors,  the  in- 
ternal resistance  increases,  thereby  decreasing  the  current.  The 
current  becomes  strong  again  upon  removing  the  gases  either 
mechanically  or  chemically.  The  greatest  collection  of  bubbles 
is  at  that  pole  which  in  sulphuric  acid  or  other  decomposable 
compound  of  hydrogen  is  where  the  hydrogen  is  liberated.  By 
means  of  the  double  electrolyte  cell  a  chemical  is  furnished 
with  which  the  hydrogen  unites  as  soon  as  liberated,  thereby 
preventing  the  formation  of  bubbles.  Those  liquids  which  can 
furnish  oxygen,  chlorine  or  similar  substance  with  which  hydro- 
gen will  unite  are  suitable  for  the  second  electrolyte.  Some 
such  compounds  are:  Nitric  acid,  HN  03;  aqueous  or  acid 
solutions  of  salts,  such  as  potassic  bichromate,  potassic  chlorate, 
sodic  chloride,  ammonic  chloride,  &\ 

Almost  any  chemical  reactions  known  in  chemistry  for 
producing  either  oxygen  or  chlorine  are  applicable  in  the  cell 
for  the  chemical  removal  of  hydrogen  bubbles.  The  name 
given  to  the  bad  action  of  the  bubbles  is  polarization,  because 
it  corresponds  to  electrically  connecting  the  poles  of  a  weaker 
cell  in  opposition.  Two  currents  are  tending  to  flow  in  opposite 
directions,  the  differences  between  the  two  being  the  resultant 
or  useful  current. 

Another  chemical  way  of  preventing  the  bubbles  is  by  using 
as  the  second  electrolyte  those  particular  salts  which  liberate  a 
pure  metal  instead  of  hydrogen.  The  metal  forms  a  coating 
which  is  a  good  conductor;  therefore  the  resistance  is  not 
increased. 

The  following  list  of  metals  serves  to  predict  upon  which 
electrode  the  hydrogen  is  given  off  in  a  primary  ceM.  If  any  two 
are  employed  in  the  order  named,  the  first  one  of  the  pair  is  the 
hydrogen  electrode  :  Silver,  copper,  antimony,  bismuth,  nickel, 
iron,  lead,  tin,  cadmium,  zinc. 

Some  of  the  ways  in  single  electrolyte  cells  of  removing  the 
bubbles  mechanically  are  by  agitating  the  electrolyte;  by 
rubbing  the  electrode,  or  by  covering  it  with  platinum  black  or 
similar  substance,  which  will  absorb  the  hydrogen,  and  by  having 
a  greatly  enlarged  electrode,  especially  as  to  the  amount  of  sur- 
face exposed  to  the  electrolyte  in  proportion  to  that  of  the  other 
electrode. 


97 

Electrodes  placed  in  the  ocean  form  a  good  cell,  because 
the  motion  of  the  salt  water  washes  off  the  bubbles  as  soon  as 
formed. 

Sometimes  the  polarization  is  so  great  with  cells  in  series 
that  it  causes  the  poles  of  some  of  the  cells  to  be  reversed;  but 
the  poles  of  a  single  cell  never  become  reversed.  Short-circuit- 
ing is  one  of  the  principal  causes  of  reversal.  The  polarization 
then  becomes  the  maximum,  causing  the  greatest  counter- 
current.  When  the  cells  are  not  duplicates  in  size  or  chemical 
nature,  &c.,  reversal  occasionally  occurs. 

When  common  moist  earth  is  mixed  with  ammonic  chloride 
(sal  ammoniac)  and  electrodes  of  copper  and  zinc  are  immersed 
therein,  a  cell  is  formed  having  but  little  polarization.  The 
hydrogen  bubbles  are  thought  to  be  absorbed  in  the  porous 
earth.  Powdered  carbon  in  large  quantity  serves  as  a  partial 
depolarizer  in  view  of  the  comparatively  large  amount  of  pores 
for  absorbing  the  hydrogen,  and  because  the  oxygen  absorbed 
from  the  air  unites  with  the  hydrogen. 

The  forcing  of  air  into  a  liquid  through  a  tube,  whereby  the 
electrolyte  is  effectually  agitated,  assists  greatly  in  depolarizing. 
The  quiet  addition  of  oxygen  to  the  electrolyte  by  mixing  without 
any  chemical  combination  with  the  electrolyte  does  not  assist  in 
depolarizing. 

The  generation  of  electricity  by  the  use  of  oxygen  in  the  air 
is  obtained  by  using  carbon  as  one  of  the  electrodes  and  a  metal 
as  the  other  electrode.  The  oxygen  is  absorbed  in  the  pores  of 
the  carbon  and  there  unites  with  the  hydrogen,  which  is  liberated 
at  the  carbon  electrode.  The  oxygen  continually  feeds  itself 
from  the  air  into  the  carbon.  When  the  carbon  is  under  such 
a  condition  as  to  receive  no  air,  the  weakness  of  the  cell  is  very 
noticeable. 

Electrodes  may  be  of  the  same  conducting  solid,  if  im- 
mersed in  different  liquids  which  are  so  arranged  as  to  gradually 
mix.  Example:  Divide  a  vessel  into  two  parts  by  an  earthen- 
ware partition,  and  place  potassic  hydrate  and  sulphuric  acid  in 
the  respective  compartments.  Place  platinum  electrodes  there- 
in, and  a  cell  is  obtained. 

Different  gases  may  also  be  employed  in  place  of  the  liquids, 
but  a  liquid  must  also  be  used  between  the  gases,  and  the  elec- 
trodes must  be  in  contact  with  both  the  liquid  and  the  gases. 
Example  :  Invert  tubes  of  hydrogen  and  oxygen  respectively 
over  and  in  dilute  sulphuric  acid,  and  use  platinum  electrodes 
which  pass  up  through  the  electrolyte  into  the  gases.  A  cell  is 
obtained,  as  may  be  known  by  connecting  the  electrodes  electri- 
cally through  a  galvanometer. 


Zinc  is  soluble  in  sulphuric  acid,  but  when  coated  with  a 
layer  of  mercury,  as  may  be  done  by  dipping  it  in  mercury  for  a 
few  minutes  after  having  dipped  it  into  some  sulphuric  acid,  it 
becomes  practically  insoluble  in  the  acid;  but  it  may  then  be 
caused  to  dissolve  in  the  acid  if  connected  electrically  with 
some  other  metal  or  carbon  also  in  the  acid. 

It  becomes  of  importance  to  study  into  the  molecular  actions 
which  are  thought  to  take  place  in  the  decomposition  of  a  liquid 
by  passing  an  electric  current  through  it.  Let  sodic  chloride 
(common  salt)  in  solution  in  water  be  considered.  It  is  supposed 
that  the  atoms  of  sodium  and  chlorine  while  in  solution  are 
not  all  permanently  combined,  but  are  continually  uniting  and 
separating,  so  that  during  any  given  minute  there  exists  not  only 
sodic  chloride,  but  also  the  separated  elements.  When,  how- 
ever, the  salt  is  dried  so  as  to  become  a  solid,  the  chlorine  and 
sodium  unite  permanently  until  again  dissolved  in  water  or 
other  liquid.  Again,  the  atoms  of  hydrogen  and  oxygen  of 
liquid  water  are  continually  combining  and  separating,  but 
in  ice  the  atoms  are  permanently  combined.  So  with  all 
conducting  compound  liquids  it  is  supposed  that  different  atoms 
composing  the  same  are  both  combined  and  separated,  but  all 
the  time  substantially  as  close  together;  /.  e.,  the  atoms  do  not 
escape  as  a  gas.  This  supposition  is  necessary  or  else  it  is 
difficult  to  grasp  the  reason  why  an  electric  current  decomposes 
liquids.  By  the  use  of  the  supposition  the  phenomenon  of 
electrolysis  is  easily  explained.  When  the  current  passes 
through  water,  the  atoms  of  hydrogen  and  oxygen  being  rela- 
tively electro  positive  and  negative,  become  charged  so  that  they 
go  to  the  respective  electrodes  and  remain  separated  as  long  as 
charged.  They  will  go  together  again  upon  cutting  off  the  cur- 
rent and  allowing  them  to  generate  a  current  as  in  the  ordinary 
oxy-hydrogen  voltmeter.  The  supposition  or  hypothesis  ex- 
plains also  why  a  liquid  becomes  a  better  conductor  when 
heated.  The  heat  increases  what  might  be  called  the  liquidity 
of  the  liquid.  It  makes  the  force  of  cohesion  less,  so  that  the 
hydrogen  and  oxygen  (in  case  of  water)  will  more  easily 
separate.  It  is  thought  from  the  above  considerations  that  the 
atoms  separate  from  one  another  under  the  influence  of  a  cur- 
rent as  a  result  of  mechanical  motion  produced  by  the  current. 
The  theory  explains  all  the  phenomena  of  electrolysis.  Solid 
compounds  are  not  decomposable  by  the  passage  of  a  current 
because  the  atoms  are  permanently  combined;  they  do  not,  as 
in  liquids,  alternately  combine  and  separate.  The  force  of 
cohesion  between  them  is  greater  and  greater  the  lower 
the  temperature;  but  with  liquids  the  forces  of  cohesion  and 


chemical  attraction  are  more  nearly  balanced  than  in  any  other 
form,  as  pointed  out  in  the  chapter  on  heat.  The  force  due  to 
electrical  molecular  repulsion  overcomes  gradually  the  force  of 
cohesion.  It  might  properly  be  called  heat  without  rise  of  tem- 
perature; because  heat  also  causes  decomposition  of  water.  The 
electric  current  decomposes  the  water  or  other  conducting  com- 
pound liquids  with  practically  no  rise  of  temperature  in  com- 
parison with  that  of  over  1,000°  required  by  heat.  As  far  as 
total  effects  are  concerned,  however,  heat  and  electric  separation 
are  similar.  As  soon  as  a  compound  arrives  at  a  certain  high 
temperature  the  decomposition  takes  place  in  the  whole  mass; 
but  with  the  electric  current  the  decomposition  is  very,  very 
slow,  gradual  and  local.  Deposition  of  metal  from  a  solution  of 
its  salt  may  not  only  be  effected  by  passage  of  a  current  through 
two  electrodes  separated  from  each  other  in  the  solution,  but  by 
the  mere  immersion  of  certain  metals  in  the  solution.  When  a 
rod  of  zinc  is  placed  in  an  acid  solution  of  stannous  chloride, 
the  tin  leaves  the  chloride  and  forms  in  crystals  upon  the  sur- 
face of  the  zinc.  Mercury  separates  silver  in  large  quan- 
tities and  quite  rapidly  from  a  solution  of  argentic  nitrate. 
Zinc  in  plumbic  acetate  soon  looks  like  a  beautiful  tree 
of  lead  scales.  The  principle  underlying  the  action  is  that 
the  metal  placed  in  the  solution  of  a  second  metallic  salt 
takes  the  place  of  said  second  metal.  Thus,  if  iron  is 
placed  in  cupric  sulphate  the  equation  is  as  follows:  Fe 
(iron)  plus  CuSC>4  (cupric  sulphate)  equals  (copper)  plus 
FeSO4  (ferric  sulphate).  Consequently,  in  order  to  get  out 
the  copper  from  the  solution,  iron  must  be  put  in  the  place 
of  the  copper. 

An  electric  cell  in  which  the  electrolyte  is  an  aqueous  solu- 
tion of  chromic  chloride,  and  the  electrodes,  tin  and  platinum, 
gives  no  current  at  the  ordinary  temperature;  but  if  heated  con- 
siderably, a  current  is -produced  in  a  closed  circuit.  The  chemi- 
cal action  consists  in  the  conversion  of  the  tin  into  stannic 
chloride.  When  the  cell  is  cooled,  it  returns  to  its  original 
chemical  condition,  and  when  heated  a  current  is  again  given 
off;  and  the  operation  may  be  repeated  indefinitely  without  loss 
of  material,  provided  the  cell  is  made  air-tight,  so  that  no  chlorine 
shall  escape.  When  the  tin  is  each  time  liberated  from  the 
stannic  chloride  it  falls  to  the  bottom  as  a  metallic  precipitate. 
The  bottom  of  the  cell  should  therefore  be  employed  from  the 
beginning  as  the  support  for  the  tin.  This  is  an  example  of  the 
conversion  of  heat  into  electricity.  Another  example  is  as  fol- 
lows :  The  electrolyte  is  melted  potassic  nitrate;  the  electrodes, 
carbon  and  iron.  The  carbon  unites  with  the  oxygen  from  the 


100 

nitrate,  forming  a  carbon  di-oxide.     The  heated  nitrate  causes 
the  conversion  of  heat  into  electricity. 

The  obtaining  of  electricity  by  the  consumption  of  carbon 
without  heat  is  illustrated  by  the  cell  in  which  sulphuric  acid  is 
one  electrolyte,  and  graphite  and  platinum  the  electrodes;  the 
acid  containing  also  a  small  proportion  of  potassic  chlorate,  as 
the  second  electrolyte.  The  potassic  chlorate  may  be  replaced 
by  peroxide  of  chlorine.  The  graphite  may  be  replaced  by 
ordinary  battery  carbon.  The  carbon  gradually  disappears. 

It  is  a  singular  phenomenon  that  with  continuous  and 
uniform  currrents,  the  nerves  in  a  human  body  are  not  as 
sensitively  affected  as  if  the  same  current  is  interrupted.  A 
shock  is  felt  if  the  current  is  rapidly  alternated,  closed  and 
opened,  or  undulated  or  vibrated  in  any  manner.  An  irritation 
of  the  nerves  of  the  tongue  by  an  electric  current  produces  a 
sensation  of  taste,  and  so  also  the  exciting  of  other  organs  pro- 
duces their  peculiar  sensations.  Even  after  death  the  nerves 
may  be  contracted.  Certain  cases  are  reported  in  which  life 
was  restored  by  exciting  the  respiratory  muscles. 

Of  all  chemical  elements,  carbon  is  the  only  one  which  has 
not  been  melted  by  means  of  the  electric  current,  but  it  has 
been  heated  to  such  a  high  temperature  by  the  current  as  to  weld 
two  pieces  together,  the  carbon  becoming  soft  while  hot,  like 
wrought  iron.  With  ordinary  commercial  electric  lighting  currents 
wire  of  any  metal  may  be  melted,  and  even  volatilized,  in  which 
condition  they  burn  by  uniting  with  the  oxygen  of  the  air,  forming 
oxides.  Differently  colored  flames  are  produced  according  to 
the  metal  burned.  Platinum  and  iron,  tin  and  zinc  give  approxi- 
mately white  light.  A  metallic  sheet  held  in  front  of  an  alternat- 
ing or  intermittent  current  magnet  becomes  hot  in  proportion 
to  the  strength  of  the  current,  while  the  magnet  remains 
comparatively  cool.  The  eddy  or  Foucault  currents  in- 
duced in  the  plate  are  the  cause  of  its  being  heated. 
A  metallic  core  put  within  a  vibratory  current  magnet  also 
becomes  hot. 

Two  plates  of  the  same  metal  which  have  just  served  to  con- 
duct a  current  into  and  out  of  a  conducting  compound  liquid, 
can  of  themselves  furnish  a  current  through  an  electric  con- 
ductor, connecting  the  two  plates. 

If  the  two  plates  are  lead,  and  the  liquid,  dilute  sulphuric 
acid,  the  electricity  thus  stored  is  due  to  the  electrolytic  forma- 
tion upon  the  respective  plates  of  the  peroxide  of  lead  and  the 
pure  reduced  lead.  After  the  passage  or  exit  of  the  stored  cur- 
rent, the  lead  has  united  with  oxygen  and  become  a  lower  oxide 
of  lead,  while  the  peroxide  of  lead  parts  with  its  oxygen  and 


101 

becomes  the  lower  oxide  of  lead  also.     Local  actions  convert 
lead  into  the  objectionable  sulphate  of  lead. 

The  storage,  so-called,  of  electricity  by  the  ordinary  storage 
battery  is  not  a  correct  statement.  The  electricity  in  passing 
from  one  lead  plate  to  another  forms  new  chemical  compounds. 
The  subsequent  chemical  affinity  during  discharge  causes  new 
compounds  to  be  formed  with  accompanying  electricity.  In 
brief,  the  electrical  force  is  converted  into  chemical  force,  which 
remains  as  long  as  desirable.  Subsequently,  the  chemical  force 
is  converted  into  electrical  force. 

Any  chemical  compound  of  a  metal  attached  to  one  electrode 
and  capable  of  uniting  with  oxygen,  when  coupled  electrically 
with  a  second  electrode  provided  with  a  chemical  compound  of 
the  same  metal  capable  of  uniting  with  hydrogen,  will,  in  an 
electrolyte  containing  hydrogen  and  oxygen  (for  example,  water 
containing  a  solution  of  the  salt  of  said  metal),  generate  an 
electric  current,  whether  these  chemicals  have  been  produced  as 
in  storing  electricity  or  by  any  other  manner  known  or  unknown. 

To  store  electricity  consists,  therefore,  in  producing  chemi- 
cal changes  in  given  compounds  and  using  the  new  com- 
pounds in  such  a  manner  as  to  produce  an  electric  current,  or 
else  it  consists,  as  in  the  case  of  the  Leyden  jar,  in  charging  a 
metallic  mass  with  electricity  while  separated  from  a  second 
metallic  mass  by  glass  or  similar  insulator.  When  the  two  are  elec- 
trically or  metallically  joined,  the  stored  electricity  is  obtained 
for  use. 

The  metals  and  alloys  which  have  been  electrically  welded 
to  themselves  are:  Gold,  silver,  silicon,  phosphor  and  aluminium- 
bronze  ;  brass,  bismuth,  copper,  zinc,  platinum,  malleable 
wrought  and  cast  iron  ;  antimony,  magnesium,  lead,  manganese, 
alloy  of  aluminium  and  iron  ;  gun  metal,  German  silver, 
fusible  metal,  crescent,  Bessemer,  stub,  chrome,  musshet  and  cast 
steel,  and  tin.  Example  :  Lead  has  been  electrically  welded 
to  lead;  gold  to  gold,  &c.  '  Different  metals  which  have  been 
welded  together  are:  Copper  to  either  gold,  silver,  Ger- 
man silver,  iron  and  brass;  brass  to  either  soft  steel, 
tin,  German  silver,  cast  iron;  wrought  iron  to  either  soft 
or  cast  steel,  tool  steel,  crescent  steel,  cast  brass,  German 
silver;  gold  to  either  platinum,  silver,  German  silver  and  silver 
to  platinum. 

Electric  welding  may  not  only  be  effected  by  the  alternating 
current,  but  also  by  continuous  currents. 

When  an  electric  conductor  is  heated  by  an  electric  current, 
the  center  of  the  same  is  the  hottest,  the  temperature  being  less 
and  less  toward  the  outer  surface. 


102 

If   two  small  bars  of   different  metals-^best  for  the   purpose 
being  antimony   and  bismuth — be   laid   upon   each   other  and 
crosswise   and  soldered  together,  an   instrument  is  obtained  by 
which  a  small  electric   current  may  be  converted  into  "cold;  " 
/.  <?.,  if  the   current  is   in  one   direction  the  temperature  of  the 
joint  is  lowered   about  4°.     When   the  current  is  reversed,  the 
temperature   of  the  joint   is  increased  an  equal   amount.     The 
reverse  of  the  above   principle  is   true.     If  the   joint  is  heated 
while   the  ends   of  the   bars   are   connected  by  a  conductor,  a 
current  of  one  direction  is  generated.  A  current  of  the  opposite 
direction  is  produced  if  the  joint  is  cooled.     With  a  very  deli- 
cate  galvanometer  a  current  is  found  to  be  produced,  however 
small  the  amount  of  heat  added  to  or  subtracted  from  the  joint. 
Why  the  cold  is  produced  is  no  better  known  than  why  heat  is 
produced    by   the   passage   of  currents   of   opposite   direction 
through  the  joint;  but  if  the  theory  of  heat  is  right,  the  matter 
is  explained  by  a  consideration  of  the  motion  of  the  molecules. 
In  the   one  case  the  motions  of  the  molecules   are  accelerated, 
producing  heat;  in  the  other  case  they  are  retarded,  resulting  in 
cold.     Another  way  in  which  the  temperature  of  a  conductor  is 
affected    is    illustrated    by   the   following   statement:   When   a 
metallic  bar  is  heated  at  one  end  and  cooled  at  the  other,  the 
temperature  of  the  bar  is  raised  to  different  amounts  according 
to  the  direction  of  the  current.     The  variation  is  so  slight  that 
it  can  be  detected  only  by  very  sensitive  means.     The  two  ends 
may  be  respectively  heated  and  cooled  to  fixed  temperatures  by 
boiling  water  and  ice.     A    differential   arrangement   will   best 
show  the  difference.     Use  two  parallel  bars,  for  example,  of  iron. 
Connect   one   pair  of  ends  by  a  wire   in  boiling  water  and  the 
other  leave  separate  in  ice  water.     Pass  a  current   through  the 
bars  by  connecting   the  unjoined  ends  to  an  electric  generator. 
Corresponding  parts  of   the  two  bars  will  be  found  to  have  very 
slightly  different  temperatures.     The  current  should  be  strong 
enough   to  heat  both   bars.     It  will   be  noticed  by  this  arrange- 
ment that  the  current  passes  through  one  bar  from  its  cool  end 
to   the   hot,  and   through   the  other   from   its   hot  end  to  the 
cold. 

With  the  same  current,  a  wire  in  a  vacuum  becomes  much 
hotter  than  if  the  wire  is  surrounded  by  a  gas,  liquid  or  solid. 
The  surrounding  material  conducts  the  heat  away  rapidly,  while 
in  a  vacuum,  the  heat  is  conducted  away  only  slowly  by  the  con- 
ductors leading  to  the  wire.  In  both  cases,  of  course,  substantially 
equal  amounts  of  heat  are  given  away  by  radiation.  A  given 
current  will  heat  a  round  wire  more  than  a  flat  one  of  the  same 
cross-section,  because  the  latter  has  a  greater  radiating  eurface. 


103 

Heat  is  produced  by  an  electric  spark.  The  electromotive  force 
for  an  arc  lamp  must  be  comparatively  high  on  account  of  the 
high  counter-electromotive  force.  This  counter-pressure  is 
similar  to  the  counter-electromotive  force  produced  by  polariza- 
tion in  an  electric  battery.  In  both  instances  it  depends  largely 
upon  the  nature  of  the  electrodes.  In  an  arc  lamp  with  carbon 
electrodes  it  is  36  volts;  with  iron  and  copper,  24;  with  zinc, 
19;  and  cadmium,  10.  The  temperatures  of  the  ends  of  the 
two  electrodes  are  widely  different,  although  heated  by  the  same 
spark;  that  of  the  positive  being  between  2,500°  and  3,500°  C., 
and  that  of  the  negative,  between  2,000°  and  2,500°.  The 
minimum  resistance  of  the  heated  air  and  gases  between  the  elec- 
trodes is  found  to  be  i  ohm,  increasing  to  15  sometimes.  Let 
two  wires  of  different  metals  touch  each  other.  A  current  in 
one  direction  cools  the  joint,  while  a  current  in  the  opposite 
direction  heats  the  joint. 

Mechanical  motion  is  directly  convertible  into  electricity  by 
friction.  The  electricity  thus  produced  is  exactly  the  same  as 
if  obtained  by  chemical  action,  but  the  pressure  is  always 
thousands  of  times  greater  and  the  total  energy  is  very  small  in 
comparison  to  the  amount  of  power  producing  the  friction. 

In  the  science  of  electricity  often  appear  the  terms  positive 
and  negative  electricity.  This  arises  from  the  introduction  of  a 
theory  that  electricity  consists  of  two  fluids  capable  of  motion. 
When  both  together  the  motion  is  zero.  When  separated  so  far 
as  not  to  have  sufficient  power  to  overcome  any  existing  resist- 
ance between  them,  they  are  at  rest.  During  the  operation  of 
their  joining  each  other  a  current  is  produced.  Similarly  are 
heard  the  terms  positive  and  negative  poles  of  a  generator. 
One  electricity  comes  from  one  and  the  other  from  the  other 
pole.  When  separated,  the  two  electric  fluids  stand  still.  This 
theory  does  not  agree  with  all  facts;  but  it  has  taken  strong 
hold  upon  the  science,  and  serves  at  least  as  a  convenient  way  of 
explaining  most  electrical  effects. 

The  substances  named  as  follows  are  in  such  an  order  that 
each  becomes  negatively  electrified  when  rubbed  with  any  of  the 
bodies  following,  and  positively  electrified  when  rubbed  with 
any  of  the  bodies  preceding  it :  Gutta-percha,  sulphur,  resin, 
sealing-wax,  caoutchouc,  metals,  wood,  silk,  cotton,  glass,  rock 
crystal,  ivory  and  flannel.  Illustration:  If  shellac  is  rubbed 
with  flannel,  the  former  will  attract  a  small  pith-ball  suspended 
by  a  silk  thread,  and  is  therefore  said  to  be  negatively  charged. 
The  flannel  will  repel  the  pith-ball  and  is  said  to  be  charged 
positively.  Glass  is  positively  electrified  when  rubbed  with  silk, 
while  the  silk  is  negatively  electrified. 


104 

A  bird  cage  containing  a  bird  may  be  charged  with  such  a 
heavy  charge  of  static  electricity  as  would  kill  the  same  bird 
outside  of  the  cage  ;  illustrating  that  static  electricity  dis- 
tributes itself  on  the  outer  surface  of  objects.  A  hollow  sphere 
having  a  small  hole  and  charged  shows  no  charge  inside  the 
sphere.  This  rule  has  its  modifications.  An  object  within  an 
object  is  capable  of  electrification.  Again,  if  two  charges  of 
positive  and  negative  electricity  are  passed  through  a  metallic 
conductor,  the  whole  mass  becomes  charged. 

Let  a  large  mass  such  as  a  piece  of  metal  mounted  upon  a 
dry  glass  rod  be  charged.  Electricity  may  be  taken  from  it  in 
small  quantities,  as  water  from  a  pail,  by  touching  it  with  a 
small  piece  of  metal  mounted  upon  glass.  The  small  piece 
will  be  found  to  be  charged  with  electricity.  If  touched  to 
another  large  discharged  metallic  mass,  as  to  a  gas  pipe,  it  be- 
comes discharged,  when  it  will  take  another  small  amount  from 
the  first-named  mass  as  before. 

The  rate  with  which  a  mass  may  be  discharged  depends, 
among  other  things,  upon  its  shape  ;  if  angular,  its  discharge 
is  quicker  than  if  continuously  curved  like  a  ball.  If  provided 
with  numerous  sharp  points,  the  discharge  occurs  most 
rapidly. 

When  a  highly  charged  body  has  a  film  of  oil  or  water  upon 
its  outer  surface,  a  shower  is  formed  in  consequence  of  the  repul- 
sion occurring  among  the  particles  of  the  liquid.  Similarly,  a 
candle  flame  brought  near  the  body  is  repelled  as  if  by  blowing 
upon  it  with  a  current  of  air.  A  light  wheel  having  tangential 
sharp  wire  points  rotates  when  delicately  pivoted  and  charged. 
The  charges  should  be  strong,  such  as  are  produced,  for  ex- 
ample, by  a  Holtz  electrical  machine,  or  lightning,  or  Leyden 
jar. 

Particles  of  dust  in  the  air  serve  to  discharge  a  body  of  its 
electricity.  Each  particle  becomes  charged,  floats  away;  other 
particles  do  the  same,  and  so  a  circulation  is  maintained  until 
the  particles  have  distributed  the  electric  charge  to  distant  ob- 
jects and  the  earth.  Illustration:  Fill  a  glass  jar  with  a  fine 
powder,  preferably  smoke,  such  as  may  be  made  from  burning 
a  little  turpentine.  Charge  these  particles  electrically,  as  by  a 
wire  connected  with  the  electrical  machine.  The  particles  keep 
carrying  off  the  electric  charge  until  they  are  all  repelled  and 
rest  upon  the  sides  of  the  jar,  leaving  the  atmosphere  therein 
very  soon  comparatively  clear. 

A  fine  powder  is  transferred  trom  one  plate  to  another 
analogously  to  electroplated  metal  by  charging  the  two  plates 
respectively  with  positive  and  negative  static  electricity.  The 


105 

particles  become  charged  with  the  same  kind  of  electricity  as 
the  plate  upon  which  they  rest,  and  are  therefore  repelled,  and 
at  the  same  time  attracted  by  the  opposite  kind  of  electricity  of 
the  other  plate. 

The  difference  between  the  ordinary  chemical  storage  bat- 
tery and  a  condenser,  both  of  which  are  electrical  accumulators, 
is  that  in  the  former  the  electricity  is  transformed  temporarily 
into  chemical  force,  while  in  the  latter  the  electricity  remains 
electricity,  and  is  accumulated  in  the  sense  that  a  great  deal 
exists  on  a  comparatively  small  surface. 

The  simplest  form  of  condenser  is  probably  that  which  con- 
sists of  a  large  plate  of  glass  having  pieces  of  tin-foil  pasted 
upon  opposite  sides,  with  a  blank  margin  of  at  least  an  inch. 
Connect  the  tin-foils  with  the  electric  machine  and  earth 
respectively.  Soon  the  accumulation  is  so  great  that  the  con- 
denser, even  after  a  few  moments,  will  give  a  longer  spark  than 
the  machine.  Any  device  is  a  condenser  which  consists  of 
conductors  separated  slightly  by  a  non-conductor.  The  layer 
of  insulation  serves  as  a  resistance  which  makes  it  more  difficult 
for  the  electricity  to  escape  to  the  earth.  It  is  analogous  to 
storing  water  by  carrying  it  from  the  ocean  to  the  top  of  a 
mountain.  Work  is  thus  stored  up,  which 'will  be  given  out 
again  when  the  water  is  allowed  to  fall  upon  a  water-wheel. 

A  condenser  is  kept  charged  by  supporting  the  same  on  an 
insulator.  It  is  discharged  by  electrically  connecting  the  two 
sheets  of  tin-foil. 

The  thinner  the  insulating  plate  between  the  tin-foils,  the 
greater  the  capacity,  which  is  also  greater,  the  larger  the  sur- 
faces of  tin-foil  and  insulating  plate;  but  with  any  given  con- 
denser, its  capacity  is  limited  to  a  fixed  amount,  howsoever 
large  the  charging  electrical  machine. 

Let  the  condenser  be  so  constructed  that  the  glass  and  tin- 
foils may  be  taken  apart  while  charged.  The  tin-foils  are  found 
to  be  substantially  void  of  electricity,  and  yet  when  put  together 
again,  a  shock  is  received  by  touching,  simultaneously,  both 
pieces  of  tin-foil.  The  action  of  the  tin-foil  results  in  the 
distribution  and  accumulation  of  the  electricity  upon  a  large 
surface  on  each  side  of  the  glass. 

Experiment  shows  that  after  discharge  of  a  condenser  a 
residue  reappears  after  a  few  minutes.  Let  the  residue  be 
discharged.  After  a  few  minutes  a  second  residue  comes,  and 
so  on  for  four  or  five  times.  The  residues  are  very  slight,  but 
they  show  that  the  glass  has  the  power  of  absorbing  some  of  the 
electricity.  Exactly  what  happens  to  the  glass  as  a  mass,  or  as 
to  its  molecules,  is  not  fully  known.  Other  insulating  plates 


106 

between  the  tin-foils  or  between  other  thin  metallic  plates  ex- 
hibit the  same  property  of  absorption.  The  amount  of  residues 
depends  upon  the  amount  of  charge,  upon  the  nearness  of  con- 
tact of  the  elements,  upon  the  material  of  which  they  are 
made  and  upon  the  thinness  of  the  insulator.  If  the  foil,  is 
replaced  by  a  liquid  conductor,  such  as  dilute  sulphuric  acid,  as 
may  be  done  by  a  change  in  the  mechanical  construction  of  the 
condenser,  the  residual  charge  is  found  to  exist  after  a  few 
moments;  but  if  the  liquid  is  given  a  shock  right  after  the  first 
discharge,  the  residual  charge  may  be  detected  within  a  few 
seconds  instead  of  minutes.  The  device  may  be  made  of  two 
concentric  glass  vessels  of  slightly  different  sizes  placed  one 
within  the  other,  and  containing  sulphuric  acid. 

If  two  pieces  of  gold-leaf  are  held  together  at  one  end,  they 
spread  apart  when  electrified.  They  become  thereby  charged 
with  the  same  same  kind  of  electricity  and  repel  each  other. 
Motion  is  therefore  one  of  the  effects  of  frictional  electricity. 

When  large  amounts  of  static  electricity  are  desired,  the 
Leyden  battery  is  used,  which  consists  of  several  condensers 
connected  in  series. 

If  a  condenser  is  discharged  through  a  conductor,  as  may  be 
done  by  connecting  the  pieces  of  tin-foil  with  a  wire,  the  cur- 
rent which  passes  is  continuous,  but  not  uniform.  It  is  vibratory. 
It  is  similar  to  releasing  a  spring  from  tension;  it  has  a  contin- 
uous but  oscillatory  motion  until  it  comes  to  rest. 

If  a  condenser  is  discharged  through  the  air  by  using  two  con- 
ductors each  touching  a  tin-foil,  but  not  quite  touching  each 
other,  the  discharge  is  abrupt,  and  the  current  formed  is  inter- 
mittent, consisting  of  a  rapid  succession  of  small  impulses. 

Electricity  has  an  effect  upon  the  human  body  and  upon 
animals  in  general.  Beginning  with  small  and  taking  gradually 
greater  and  greater  shocks,  the  elbows  feel  it  first  most  strongly, 
then  the  chest,  and  finally  the  stomach.  An  army  of  1,500  men 
once  took  a  shock  by  joining  hands.  They  felt  it  strongly. 
Those  at  and  nearest  the  center  get  the  least  shock,  which  is 
explained  that  some  leaks  to  earth  before  the  central  men  re- 
ceive it.  The  discharge  of  a  large  battery  may  be  retarded  by 
passage  through  a  wet  rope. 

The  spark  which  is  formed  by  the  disruptive  discharge  Jias 
different  colors  according  to  the  nature  of  the  terminals,  and 
some  of  the  material  is  volatilized  and  passes  from  one  pole  to 
the  other.  Thus,  with  gold  and  silver,  some  of  the  silver  is 
deposited  upon  the  gold,  and  some  of  the  gold  upon  the  silver. 
Carbon  terminals  give  a  yellow  spark;  ivory,  a  beautiful  red, 
and  copper,  green,  especially  if  the  copper  is  first  covered  with 


107 

a  coating  of  silver.  The  color  varies  also  with  the  nature  of 
the  gas  in  which  the  sparking  occurs.  In  a  vacuum  it  is  violet; 
in  hydrogen,  red;  in  the  ordinary  atmosphere,  white;  in  a 
partial  vacuum,  red;  in  oxygen,  white;  and  in  mercury  vapor, 
green.  When  the  spark  is  produced,  a  sound  occurs,  whose  in- 
tensity depends  upon  the  magnitude  of  the  cause  of  the  spark. 
As  is  well  known,  in  the  case  of  lightning,  the  noise  is  very 
great.  Even  with  slight  sparks  the  noise  is  quite  striking  and 
peculiar  when  made  in  nitrogen  gas.  The  sound  in  all  cases  is 
due  to  vibrations  communicated  to  the  air.  When  the  spark 
occurs,  the  gas  is  momentarily  intensely  heated,  causing  a  rare- 
faction. On  suddenly  cooling,  condensation  of  the  air  occurs, 
and  both  taken  together  produce  the  sound.  In  addition,  the 
sound  is  also  thought  to  be  caused  by  the  spark  making  a  hole 
through  the  air,  /'.  e.,  a  vacuum;  when  the  spark  ceases,  the  air 
rushes  into  the  hole,  causing  a  condensation.  This  hole-forma- 
tion idea  is  not  at  all  unreasonable,  because  a  powerful  spark 
will  pass  through  glass  or  carboard  and  other  insulators  placed 
between  two  pointed  terminals,  and  a  very  fine  hole  is  formed, 
which  is  .so  small  as  to  be  invisible.  Make  the  hole  near  the 
bottom  of  a  glass  tube  closed  at  one  end.  Hold  the  closed  end 
under  water  and  blow  into  the  tube.  Very  small  bubbles  will 
be  seen  passing  up  through  the  water  from  the  hole. 

With  any  given  spark  it  has  the  most  light-giving  power, 
the  greater  the  intensity  of  the  discharge.  When  the  discharge 
takes  place  between  sharp  points,  the  spark  has  the  appearance 
of  a  brush;  when  between  ball-shaped  terminals,  the  spark  is 
linear,  and  often  zig-zag,  as  in  lightning,  the  earth  and  the  clouds 
being  the  balls. 

A  line  of  sparks  may  be  formed  by  letting  the  discharge  take 
place  through  successive  conductors  all  but  touching  each  other. 
Thus,  let  the  pieces  be  in  a  straight,  curved  or  zig-zag  line,  and 
at  about  .01  inch  apart.  Let  the  first  and  last  pieces  be  con- 
nected to  the  pieces  of  tin-foil  upon  the  condenser.  At  the 
ends  of  each  piece  a  spark  is  visible,  so  that  the  effect  is  that 
of  a  line  of  light.  In  this  manner  pictures  of  light  may  be  made. 

The  spark  is  accompanied  by  heat,  as  illustrated  by  pro- 
ducing a  spark  upon  a  gas  burner.  The  gas  becomes  lighted. 
Ether  may  also  be  lighted,  and  alcohol,  if  first  warmed. 

Let  the  discharge  be  made  through  a  very  fine  platinum  wire. 
The  wire  is  slightly  heated.  If  the  spark  first  passes  through 
cardboard,  the  heating  of  the  wire  is  less. 

Egg  shells  become  faintly  luminous  in  the  dark  by  first  pass- 
ing sparks  through  them.  So  do  also  fruits,  sugar,  fluor-spar, 
and  heavy  spar. 


108 

Gold-leaf  may  be  turned  into  vapor  by  pressing  the  same 
between  two  glass  plates  and  sending  a  charge  through  the  gold- 
leaf.  The  particles  of  the  gold  condense  into  a  violet-colored 
powder,  visible  through  the  glass. 

Magnetize  and  demagnetize  iron  rapidly,  it  becomes  heated; 
or  repeatedly  hammer  a  metal,  it  becomes  heated;  or  rub  a  sub- 
stance, it  becomes  heated.  Also  charge  and  discharge  a  con- 
denser rapidly,  the  glass  becomes  heated.  In  all,  the  molecules 
are  certainly  set  into  vibration. 

Independently  of  any  heating  of  the  air  or  perforation,  en- 
closed air  is  expanded  by  sparks.  If  the  terminals  are  balls, 
the  expansion  is  only  instantaneous;  if  pointed,  the  air  only 
slowly  expands. 

The  oxygen  and  nitrogen  of  the  air  may  be  caused  to  unite 
in  small  quantities  by  repeated  sparks  in  a  vessel  of  moist  air. 
Blue  litmus  paper  is  turned  red  after  the  sparks  have  been 
passed,  and  the  density  is  slightly  diminished.  The  sparks  will 
ignite  a  mixture  of  oxygen  and  hydrogen  with  the  formation 
of  water  vapor.  Coal  gas  and  oxygen  are  also  set  on  fire  by 
the  spark.  This  spark  of  frictional  or  static  electricity 
will  also  decompose  substances  as  water,  ammonic  hydrate 
(ammonia),  hydric  sulphide,  and  solutions  of  oxides  and  metal- 
lic salts;  but  the  chemical  actions  of  galvanic  electricity  (from 
the  dynamo  or  galvanic  battery)  are  much  greater  than  those  of 
static  electricity. 

The  duration  of  an  electric  spark  in  air  is  .004  second;  in 
water,  .018  second. 

The  velocity  of  electricity  is  not  accurately  known,  but  it  is 
about  the  same  as  that  of  light.  The  velocity  depends  upon 
the  nature  of  the  conductor  and  also  the  medium  around  the 
conductor.  With  an  insulated  wire  in  water  the  velocity  is  less 
than  with  such  a  wire  in  air.  The  velocity  is  independent 
of  the  electromotive  force  or  diameter  of  the  wire. 

Carbon  cannot  be  electroplated  successfully  upon  itself  or 
another  substance,  but  an  equivalent  result  is  obtained  by 
decomposition  of  a  hydrocarbon  at  a  high  temperature,  the 
carbon  forming  a  hard  coating  upon  the  incandescent 
surface. 

The  thickness  of  the  deposit  varies  in  any  given  period 
with  the  temperature  of  the  receiving  substance. 

In  any  given  electric  circuit  of  sufficient  energy  heat  may 
be  obtained  by  sufficiently  reducing  the  cross-section  of  the 
conductor,  or  by  breaking  the  circuit  and  maintaining  an  arc 
between  the  two  parts;  or  if  the  current  is  alternating,  pulsatory 
or  intermittent,  by  placing  a  second  conductor  closed  upon 


109 

itself  (like  a  ring)  as  close  as  possible  (without  touching)  to  the 
circuit  named. 

Amber  attracts  only  when  rubbed,  but  a  lodestone  always 
attracts. 

What  is  true  of  amber  is  true  of  all  substances,  which,  if 
metallic,  must  be  supported  by  good  insulation. 

Substances  attracted  by  the  magnet  are  iron  and  steel 
greatly,  and  nickel,  cobalt,  chromium,  manganese,  bismuth, 
antimony  and  zinc  very  slightly. 

Steel  retains  its  magnetism  almost  perfectly  when  removed 
from  the  magnet,  and  becomes  a  second  magnet,  while  the 
remaining  substances  (nickel,  &c.)  retain  a  mere  trace  of  resid- 
ual magnetism. 

The  laws  of  magnetic  attraction  are  the  same  as  those  of 
gravitation.  The  force  varies  inversely  as  the  square  of  the 
distance.  Example:  At  twice  the  distance  the  force  is  only  £ 
as  great. 

A  lodestone  is  always  a  magnet,  but  an  electromagnet  be- 
comes non-magnetic  upon  interrupting  the  current  which  flows 
in  the  coils  of  the  magnet. 

If  the  coils  surround  an  iron  core,  the  total  magnetism  is  no 
greater  than  without  iron;  but  the  force  is  directed  in  the  same 
direction  as  that  of  the  pole-pieces  formed  upon  the  core. 

The  force  of  gravitation  exists  not  only  between  the  earth 
and  all  substances,  but  between  and  among  any  and  all  bodies, 
and  is  always  in  the  form  of  attraction;  but  magnetism  and 
electrical  force  may  be  made  to  exhibit  themselves  either  as  re- 
pulsion or  attraction. 

Of  two  magnets,  the  unlike  poles  thereof  attract — the  like 
repel  each  other. 

Between  two  pieces  of  rubbed  substances,  as  amber,  if  the 
rubbing  is  done  with  the  same  material,  repulsion  occurs. 

Pieces  of  different  materials  rubbed  together,  while  properly 
insulated  from  the  hands  or  earth,  attract  one  another  with  a 
force  sufficient  to  overcome  that  of  gravitation. 

The  amount  of  repelling  or  attracting  force  is  greatest  in  a 
dry  atmosphere  or  vacuum  and  increases  with  the  force  of 
rubbing  and  with  the  efficiency  of  the  insulation  employed,  but 
is  limited  according  to  the  nature  of  the  material  and  the 
amount  of  surface. 

The  force  of  magnetism  may  be  steered  in  any  dirction  by 
motion  of  the  whole  magnet  or  of  the  pole-pieces  only. 

In  electric  currents  of  low  potential,  such  as  those  generated 
by  a  dynamo  or  galvanic  battery,  the  amount  of  energy  carried 
by  a  conductor  is  greater,  the  greater  the  cross-sectional  area, 


110 

while  with  frictional  electricity,  or  that  produced  by  rubbing, 
the  larger  the  exterior  surface  of  the  conductor,  the  better  the 
electricity  is  conducted. 

The  electrical  conductivity  of  a  metal  decreases  with  rise  of 
temperature  and  that  of  carbon  increases. 

Every  metal  has  a  different  degree  of  conductivity  at  the 
same  temperature,  among  the  best  being  silver,  copper,  gold  and 
zinc,  and  among  the  worst  being  platinum  and  German  silver. 

An  electric  current  may  be  set  into  vibration  by  alternately 
increasing  and  diminishing  the  resistance  at  one  or  more  points; 
by  similarly  varying  the  electromotive  force  or  pressure  of  the 
current;  by  varying  the  self-induction  or  "inductance;"  by 
varying  the  induction  between  two  or  more  conductors;  by 
varying  the  temperature  of  a  conductor  in  the  current;  by 
alternating  the  current  ;  by  alternately  interrupting  and  closing 
the  circuit ;  by  varying  the  electric  generation  of  the  cur- 
rent; by  varying  the  length  or  cross-section  of  a  conductor 
(which  may  be  solid  or  fluid)  included  in  the  circuit;  by  vary- 
ing the  pressure  upon  carbons  or  similar  semi-conductors  in 
loose  contact  and  in  the  electric  circuit;  by  alternately  cutting 
in  and  cutting  out  resistances  from  the  circuit;  by  varying  the 
degree  of  perfection  of  contact  between  two  or  more  terminals 
of  an  electric  circuit;  by  the  rising  and  falling  of  a  liquid  con- 
ductor surrounding  a  solid  conductor  partly  immersed  in  the 
liquid,  both  the  solid  conductor  and  liquid  conductor  being  in 
the  electric  circuit;  by  sliding  backward  and  forward  two  elec- 
tric terminals  while  in  contact;  by  alternately  heating  and 
cooling  a  conductor  whether  liquid  or  solid;  by  alternately  de- 
positing and  removing  a  conducting  coating;  by  varying  the 
action  of  light  upon  the  conductor,  provided  the  same  is  made 
of  selenium,  which  becomes  a  fairly  good  conductor  in  the  light 
and  loses  this  property  immediately  in  the  dark  ;  or  by  the 
action  of  light  or  heat  upon  those  substances  which  will  undergo 
a  chemical  change  when  exposed  to  light  or  heat;  by  varying 
the  .  distance  between  an  electromagnet  in  the  circuit,  and 
a  piece  of  iron,  steel  or  nickel,  or  another  electromagnet  in  the 
same  or  different  circuit;  by  varying  the  distance  between  a  per- 
manent magnet  wound  with  a  coil  closed  upon  itself  and  a  second 
piece  of  steel  or  iron  or  nickel;  by  varying  the  distance  be  ween 
two  parallel  conductors  carrying  currents  from  the  same  or 
different  generators;  by  alternately  increasing  and  decreasing 
the  length  of  a  coil  of  wire;  by  varying  the  length  of  a  spark 
between  two  electrodes  or  electric  terminals;  by  variation  of 
chemical  action;  by  varying  the  amount  of  surface  acted  upon 
by  a  liquid  or  electrolyte  in  a  galvanic  battery;  by  varying  the 


Ill 

chemical  nature  of  the  electrolyte  or  electrodes;  by  heating  and 
cooling  the  liquid  or  electrodes;  by  varying  the  distance  be- 
tween the  electrodes;  by  agitating  the  liquid;  by  varying  the 
opposing  action  of  a  second  battery  in  the  same  current;  by  the 
action  of  a  varying  quantity  or  intensity  of  heat  upon  a  con- 
ductor forming  a  part  of  the  circuit;  by  the  variations  of  tem- 
perature upon  a  thermopile;  by  the  variation  of  pressure  of  an 
atmosphere  upon  a  thermopile;  and  by  alternately  heating  and 
cooling  the  mineral  kaoline,  while  included  in  an  electric  circuit 
(this  mineral  having  the  property  of  conducting  electricity 
when  heated  and  losing  its  conductivity  when  cooled). 

A  pivoted  polarized  armature  (/.  e.,  a  permanent  steel  mag- 
net) having  one  pole  located  between  the  opposite  poles  of  an 
electromagnet  included  in  a  circuit  carrying  an  alternating  elec- 
tric current,  is  set  into  vibration  in  unison  with  the  alternations. 

An  alternating  electric  current  may  be  converted  into 
mechanical  motion  not  only  as  above,  but  a  magnet  in  circuit 
therewith  will  repel  a  mass  of  metal,  which  should  for  best 
effects  be  in  the  form  of  a  ring,  or  it  may  be  an  ordinary 
solenoid  having  its  terminals  electrically  connected.  The  coil, 
for  maximum  power,  should  be  of  large  wire. 

An  alternating,  intermittent  or  undulatory  current  may  be 
communicated  from  one  circuit  to  another  circuit  or  coil  by 
placing  the  two  close  to  each  other  without  touching.  The 
secondary  current  is  the  induced  current,  and  the  primary  is  the 
inducing  current.  The  amount  of  energy  represented  in.  the 
secondary  circuit  is  dependent  upon  the  length  of  wire  ex- 
posed to  the  influence  of  the  primary  and  upon  the  cross- 
sectional  area  of  the  wire  of  the  secondary.  The  secondary 
will  induce  a  tertiary  current  in  a  third  wire,  and  so  on 
indefinitely. 

By  having  a  very  long,  fine  primary  wire,  in  the  form  of  a 
coil,  and  a  large  but  short  secondary  wound  upon  or  within  the 
first  coil,  the  induced  current  will  be  of  low  pressure  and  great 
quantity.  An  opposite  effect  may  be  obtained  by  opposite 
conditions. 

The  motion  of  one  coil  carrying  a  continuous  or  uniform 
current  to  or  from  another  closed  coil  will  induce  or  increase  a 
current  in  the  latter,  according  to  the  relative  directions  of 
winding. 

A  great  variety  of  effects  in  vibrations  of  current  may  be 
obtained  in  a  closed  secondary  coil  by  vibrating  before  it  a  coil 
carrying  an  alternating,  intermittent  or  undulatory  current. 

Secondary,  tertiary,  &c.,  currents  have  exactly  the  same 
properties  as  the  primary 


112 

When  a  circuit  is  broken  a  spark  is  formed  at  the  point  of 
rupture,  and  its  length  or  light-giving  power  for  any  given  cur- 
rent is  increased,  the  longer  the  wire  forming  the  circuit  and 
more  yet  if  the  wire  is  coiled  into  numerous  convolutions,  and 
provided  also  the  diameter  is  as  small  as  practicable.  With  a 
large  wire  of  short  length  the  spark  is  short,  but  has  the  maxi- 
mum heating  but  minimum  lighting  power.  These  properties  of 
forming  sparks  of  different  magnitudes  as  to  light  and  heat  are 
likewise  true  in  regard  to  secondary,  tertiary,  &c.,  currents. 

When  the  electromotive  force  or  pressure  is  sufficiently  great 
a  spark  will  occur  upon  bringing  electric  terminals  toward  each 
other  to  a  distance  dependent  upon  the  electromotive  force. 

A  spark  may  be  maintained  between  two  incombustible 
terminals  or  electrodes  by  bringing  them  together  and  then 
separating  them  and  maintaining  them  at  a  fixed  distance  from 
each  other;  or  a  substantially  continuous  sparking  may  be 
obtained  by  rapidly  vibrating  the  electrodes  to  and  from  each 
other,  the  spark  being  formed  each  time  they  break  the  circuit. 

The  electric  spark  in  air  is  intensely  violet,  but  if  the  elec- 
trodes are  combustible  the  color  is  partly  changed  to  a 
mixture  of  other  colors;  when  formed  beneath  the  surface  of 
oils,  it  is  green;  in  turpentine  and  the  sulphide  of  carbon,  it  is 
white;  while  it  is  red  when  formed  in  alcohol,  and  in  general  of 
a  different  color  for  almost  every  liquid. 

The  pressure  of  enclosed  air  is  increased  by  the  transmission 
through  it  of  an  electric  spark. 

A  mixture  of  oxygen  and  hydrogen,  or  of  hydrogen  and 
chlorine  gases,  or  of  air  and  coal  gas,  or  of  any  two  or  more 
gases  capable  of  ignition  by  a  flame,  is  ignited  with  explosive 
powers  by  an  electric  spark. 

Sparks  of  greatest  length  and  of  maximum  chemical  power 
are  best  obtained  either  by  electricity  from  the  frictional  elec- 
tric machine  or  induction  coil  or  lightning,  while  sparks  of  the 
greatest  heat  and  light  power  are  best  obtained  from  the  dynamo 
or  large  galvanic  batteries. 

Iceland  spar  has  the  peculiar  property  that  when  forcibly 
and  quickly  compressed  of  becoming  charged  with  electricity, 
as  may  be  shown  in  the  dark  by  its  exhibiting  a  spark  when 
touched,  or  by  its  attracting  pith-balls  and  other  light  particles, 
all  illustrating  the  principle  that  compressure  produces  static 
electricity. 

Tourmaline  while  heating  or  cooling  has  a  charge  of  elec- 
tricity, and  so  do  some  other  substances  to  a  less  degree, 
namely  :  Axenite,  cane  sugar,  potassic  tartrate,  Pasteur's  salt, 
topaz,  phrenite,  scolezite,  zinc  silicate  and  boracite. 


113 

Sulphur  when  melted  in  a  glass  vessel  becomes  charged  with 
electricity,  as  may  be  proved  in  the  dark  by  seeing  a  slight 
spark  between  it  and  a  pith-ball  loosely  in  contact  therewith. 
Light  will  produce  static  electricity.  Thus,  place  fluor-spar  in 
the  sunlight  or  electric  light.  Heat  electrifies  it  also. 

The  first  Leyden  jar  ever  made  consisted  of  a  corked  bottle 
containing  water  and  a  wire  passing  through  the  cork  into  the 
water.  After  charging,  it  could  be  discharged  by  holding  the 
bottle  in  one  hand  and  touching  the  wire  with  the  other,  there- 
by illustrating  the  principle  that  electricity  can  be  stored  in  a 
bottle. 

Frictional  electricity  may  be  converted  into  magnetism  by 
twisting  a  fine  platinum  wire  into  a  coil,  inserting  a  fine  steel 
needle  wound  with  silk  thread,  and  passing  a  succession  of 
electric  sparks  through  the  coil.  The  needle  becomes  a  weak 
permanent  magnet. 

Upon  exposing  a  mixture  of  chlorine  and  hydrogen  to  the 
light  of  an  arc  lamp  they  combine  with  the  formation  of  hydro- 
chloric acid.  Also  the  chemical  effect  of  the  light  from  the 
spark  is  illustrated  by  its  power  to  turn  chloride  of  silver 
black. 

The  spark  produced  by  statical  as  well  as  galvanic  elec- 
tricity produces  chemical  action,  as  illustrated  by  the  fact  that 
electrodes  when  immersed  in  a  conducting  compound  liquid 
cause  decomposition.  In  the  case  of  galvanic  electricity  it  is 
not  necessary  that  the  electrodes  be  so  close  to  each  other  as  to 
produce  a  spark. 

While  it  is  true  that  upon  rarefaction  of  enclosed  air  the 
luminosity  thereof  becomes  increased,  it  has  been  lately  shown 
that  with  a  maximum  obtainable  vacuum  the  light  becomes 
extinct,  electrodes  being  supposed  to  extend  into  the  enclosed 
air  and  charged  with  frictional  electricity. 

The  spark  or  arc  and  therefore,  also,  the  resistance  of  the 
circuit  may  be  varied  by  varying  the  material  of  the  electrodes; 
the  distance  between  the  electrodes;  the  homogeneity  of  the 
structure;  the  chemical  composition  of  the  fluid  in  which  the 
arc  is  formed;  the  motion  of  the  fluid  or  the  temperature  of  the 
electrodes. 

In  any  given  arc  lamp  in  a  primary  the  positive  electrode 
becomes  of  a  higher  temperature  than  the  negative,  while  if 
in  a  secondary  current  the  opposite  is  true. 

The  following  are  the  leading  types  of  alternating  electric 
current  motors  :  (a)  An  ordinary  direct  current  series  motor 
will  operate  with  an  alternating  current,  (b)  An  alternating 
electric  current  generator  acts  as  a  motor  when  in  circuit  with 


114 

a  second  similar  generator  driven  by  mechanical  power;  but  the 
motor  is  not  self-starting,  (c)  A  motor  will  operate  in  which 
provision  is  made  for  passing  the  impulses  of  opposite  direction 
through  different  field  magnets  so  as  to  get  continuous  north 
and  south  poles,  (d)  The  combination  of  an  ordinary  alternate 
and  direct  current  motor.  (<?)  A  motor  in  which  the  magnetic 
poles  of  either  the  armature  or  field  magnet  are  not  stationary, 
but  are  progressively  shifted.  (/)  A  motor  in  which  a  closed 
coil  is  repelled  and  then  opened;  another  closed  coil  is 
repelled  and  then  opened,  and  so  on,  whereby  an  armature  is 
rotated,  (g)  Gutmann's  various  types  of  motor.  (/;)  A  motor 
in  which  the  coils  of  the  field  magnet  are  closed  upon  them- 
selves, and  in  which  the  armature  coils  are  in  circuit  with  a 
primary  or  secondary  circuit. 

It  is  important  to  remember  the  distinction  of  causes  of 
repulsion  and  attraction.  Like  magnetic  poles  repel,  but  cur- 
rents of  like  direction  attract  each  other.  Unlike  magnetic 
poles  attract,  but  currents  of  unlike  direction  repel.  Again,  in 
the  case  usually  met  in  static  electricity,  like  charges  repel  each 
other,  while  unlike  charges  attract  ;  thus,  two  pith-balls  both 
charged  with  either  positive  or  negative  repel  each  other,  but  when 
one  is  charged  with  positive  and  the  other  with  negative  electricity 
they  attract  each  other.  Upon  the  principle  of  currents  being 
attracted  or  repelled,  liquids  may  be  set  into  motion  by  so 
arranging  them  to  be  the  carrier  of  -one  or  both  of  the  currents. 
The  liquids  "may  be  caused  to  circulate.  Of  course,  the  liquid 
should  be  an  electric  conductor. 

If  a  copper  disc  is  rotated,  a  magnetic  needle,  even  at  a 
comparatively  great  distance  from  the  disc,  is  rotated.  If  a 
copper  disc  is  strongly  rotated  between  the  poles  of  a  powerful 
magnet  it  becomes  hot.  The  plane  of  the  disc  should  be 
parallel  to  the  axes  of  the  pole-pieces,  v/hich  should  be  quite 
close  together. 

An  alternating  current  is  transformed  into  a  substantially 
continuous  current  in  a  shunt  to  an  arc  formed  between  the 
terminals  of  a  secondary  coil,  the  respective  terminals  being  a 
sharp  point  and  a  ball.  The  electromotive  force  should  be 
sufficient  to  form  a  spark  discharge.  The  arc  is  accompanied 
by  a  singing  note  or  sound.  An  ordinary  Ruhmkorff  coil  and 
platinum  terminals  may  be  employed. 

Magnetization  of  iron  may  be  produced  by  successive  dis- 
charges of  a  Leyden  jar  battery.  The  best  form  for  a  tem- 
porary magnet  is  that  of  glass  tube  filled  with  iron  filings. 

An  increase  of  temperature  or  "  heat "  decreases  the 
magnetism — whether  in  iron  or  steel. 


115 

A  line  of  light  is  seen  to  pass  from  one  pole  to  the  other 
located  in  a  vacuum.  A  magnet  applied  to  the  side  of  the 
vacuum  chamber  attracts  the  line  of  light  the  same  as  if  it  were 
an  iron  wire.  On  reversing  the  current  through  the  magnet 
(/.  e.t  applying  the  opposite  magnetic  pole)  the  line  of  light  is 
repelled. 

The  continuous  line  of  light  between  the  poles  may  be 
intermitted  or  stratified  by  increasing  the  so-called  vacuum. 

Electricity  may  be  converted  into  light  and  heat  by  the  use 
of  a  condenser  made  by  placing  mica  between  sheets  of  tin-foil, 
ozone  being  formed  during  the  heating  and  formation  of  a 
luminous  layer  between  the  foil  and  mica. 

The  spark  between  the  terminals  of  a  secondary  coil  of  very 
low  resistance  (the  primary  being  of  high  resistance,  and  both 
being  of  a  good  conductor,  carries  so  much  heat  that  when  the 
spark  is  infinitesimally  small,  /.  e.,  when  the  terminals  are  in  bad 
contact,  the  same  soon  become  fused  together,  forming  as  strong 
a  joint  as  by  ordinary  welding. 

The  impulses  of  one  direction  in  an  electric  current  may  be 
sifted  from  those  of  the  other  direction,  and  at  the  same  time 
doubled,  by  passing  the  said  alternating  current  through  a 
battery  or  dynamo  of  the  same  electromotive  force  as  that  of 
the  alternating  generator. 

An  alternating  current  is  converted  into  a  direct  current  by 
a  pole-changer,  acting  synchronously  with  the  alternations. 

A  globule  of  mercury  changes  its  length  during  the  passage 
of  an  electric  current. 

A  varying  impulse  of  current  may  be  retarded  by  trans- 
mission over  a  circuit  of  many  miles — the  longer,  the  greater 
the  retardation. 

It  is  against  the  principles  of  mechanics  for  an  intermittent 
current  to  transmit  articulate  speech,  but  such  a  current  can 
transmit  musical  sounds. 

The  rapid  breaking  and  closing  of  a  current  produce  an 
intermittent  current. 

The  regular  and  rapid  varying  of  a  current  from  approxi- 
mately zero  to  maximum  produces  a  pulsatory  current. 

The  current  which  varies  in  exact  proportion  to  any  force 
which  is  the  cause  of  variation  is  an  undulalory  current. 

A  very  peculiar  manner  of  generating  a  vibratory  current 
consists  in  vibrating  a  wire  made  of  different  metals.  Such  a 
vibrating  wire  acts  as  an  electric  generator  of  minute  currents. 
When  the  vibrations  stop,  the  current  stops. 

Reeds  of  different  lengths  produce  different  musical  notes 
when  struck;  and  each  reed  will  give  but  one  note.  Therefore, 


116 

if  of  iron,  and  vibrated  in  front  of  an  electromagnet,  a  musical 
telephone  transmitter  is  obtained,  and  will  operate  a  receiver 
constructed  in  the  same  manner. 

Instead  of  acting  by  variation  of  magnetism,  as  above,  the 
current  may  be  intermitted  by  the  vibrating  reeds  in  so  far  as 
the  transmitter  is  concerned.  In  both  cases,  the  vibration  of 
any  particular  reed  in  the  receiver  will  result  in  the  vibration  of 
the  reed  of  the  same  length  in  the  receiver;  but  no  other  reed 
of  the  latter  will  vibrate. 

Among  the  semi-conductors  which  convert  sound  into  elec- 
tric vibrations  when  employed  as  loose  contacts  in  an  electric 
circuit,  as  in  the  carbon  telephone  transmitter,  are:  Platinum 
black;  paper,  whose  pores  are  filled  with  metallic  particles; 
metallic  sulphides;  cork  coverd  with  plumbago;  cupric  iodide; 
charcoal  containing  in  its  pores  platinic  perchloride;  amorphous 
phosphorus;  paper  moistened  with  a  conducting  liquid;  man- 
ganic oxide  and  plumbic  hyperoxide;  white  silver  powder;  shot 
in  a  glass  tube;  carbon  saturated  .with  mercury. 

The  best  substance  over  any  of  the  above  is  lamp-black 
mixed  with  some  adhesive  substance,  such  as  syrup,  and 
pressed  into  buttons  under  enormous  pressure  and  carbonized. 

A  glass  tube  filled  with  a  mixture  of  finely  divided  tin  and 
zinc  (white  silver  powder)  and  corked  at  the  ends  with  carbon 
terminals,  sealed  with  wax,  and  included  in  an  electric  circuit, 
is  a  sensitive  rheostat  for  minute  currents.  When  pulled  or 
compressed  a  galvanometer  or  telephone  receiver  will  indicate 
the  fluctuation  of  current  produced. 

Paper  moistened  with  a  mixture  of  potassic  iodide  with  a 
small  amount  of  starch  paste,  or  if  moistened  with  potassic 
ferricyanide,  is  sensitive  to  an  electric  current.  If  touched 
with  electric  terminals  upon  opposite  sides  of  the  paper, 
the  same  becomes  colored  blue  at  the  point  touched.  By 
moistening  the  same  with  cupric  sulphate  the  result  is  a 
blackening  of  the  paper  at  the  point  touched.  The  sub- 
stances thus  sensitive  are  those  which  are  electrolytically 
decomposable  into  new  compounds  or  elements  which  have 
a  different  color  from  the  original. 

A  diaphragm-,  pressing  upon  parallel  carbonized  silk  or 
linen  threads,  is  thrown  into  vibration  by  a  vibratory  current. 
The  parallel  currents  in  the  filaments  variably  attract  or  repel 
one  another. 

Of  two  pieces  of  selenium  included  in  an  electric  circuit, 
that  one  which  is  annealed  is  the  more  sensitive  to  light  for 
the  purpose  of  increasing  its  electrical  conductivity  by  the 
action  of  light. 


117 

Sparking  may  be  partially  eliminated  by  providing  an 
electric  condenser  or  choking  magnet  of  high  self-induction 
in  a  shunt  around  the  terminals  at  which  the  sparking  tends 
to  occur.  A  choking  magnet  is  a  long  coil  of  fine  wire  upon  an 
iron  core.  The  magnet  may  have  a  closed  secondary  coil  wound 
upon  it. 

Variation  of  a  beam  of  heat  upon  a  thermopile  does  not 
produce  immediate  and  proportional  variation  of  current  on 
account  of  sluggishness  of  heat;  but  variation  of  a  beam  of 
light  upon  selenium  in  an  electric  circuit  produces  immediate 
and  proportional  variation  of  current. 

A  musical  note,  or  at  least  a  humming,  is  produced  at  the 
arc  of  an  alternating  current  lamp;  being  produced  by  the 
rapid  extinction  and  re-establishment  of  the  current,  the  effect 
being  similar  to  that  of  "singing  flames." 

A  peculiar  manner  in  which  a  vibratory  current  may  vibrate 
a  diaphragm  is  that  in  which  the  latter  has  a  metallic  pro- 
jection resting  upon  a  moving  surface  moistened  with  a  con- 
ducting solution,  as  chalk,  containing  caustic  potash  mixed  with 
mercuric  acetate  in  the  pores  of  the  chalk.  Or  hydrogen  dis- 
odic  phosphate  may  be  used.  The  moistened  surface  forms  the 
remaining  terminal.  Variations  of  current  produce  variations 
of  friction,  and  variations  of  friction  produce  variations  of 
motion  of  the  diaphragm. 

When  the  plates  of  an  electric  condenser  are  vibrated  to 
and  from  each  other,  the  electric  charge  thereon  is  varied  in 
intensity. 

Let  one  circuit  contain  a  generator,  a  carbon  transmitter 
and  two  coils.  Let  another  circuit  contain  a  telephone 
receiver  and  two  coils  of  the  same  electrical  dimensions  as 
the  first  two  and  placed  respectively  opposite  them.  Sounds 
at  the  transmitter  are  not  heard  in  the  receiver.  Place 
a  metal  between  two  of  .the  coils;  the  sound  will  be  heard. 
The  two  coils  in  either  circuit  should  be  wound  in  opposite 
directions. 

The  closing  of  a  circuit  induces  a  momentary  extra 
current.  The  opening  of  a  circuit  induces  a  momentary  extra 
opposition  current;  both  being  the  greater,  the  greater  the 
length  of  wire,  and  especially  if  the  wire  is  coiled. 

The  amount  and  duration  of  the  extra  currents  vary  with 
different  metals,  different  molecular  structure,  and  the  form  of 
cross-section.  With  iron  the  duration  is  greatest,  and  increases 
with  the  diameter  of  the  wire.  With  carbon  the  duration  is 
practically  zero  The  duration  is  not  varied  by  changing  the 
electromotive  force. 


118 

If  the  wire  is  bent  back  upon  itself,  so  that  the  outgoing  and 
return  wires  are  as  close  together  as  possible  without  touching, 
the  extra  currents  are  nearly  cancelled. 

With  any  given  conductor  of  considerable  length,  that  in 
any  given  portion  of  cross-section  reacts  upon  that  in  the  re- 
maining portion,  illustrating  that  the  current  may  be  con- 
sidered as  constructed  of  an  infinite  number  flf  parallel  elemen- 
tary currents. 

Self-induction  and  extra  currents  are  reduced  about  80  per 
cent,  in  iron,  and  35  per  cent,  in  copper,  by  employing  thin,  flat 
ribbon  instead  of  circular  wire. 

The  extra  currents  in  a  steel  wire  are  greater  and  of  much 
greater  duration  than  in  a  flat  tape,  where  the  duration  is  scarcely 
perceptible, 

Copper-plated  iron  wire  has  less  self-induction  than  the  iron 
wire  itself. 

In  two  parallel  iron  and  copper  wires  joined  at  the  ends 
the  extra  currents  in  the  copper  wire  are  reduced  over  60  per 
cent. 

An  iron  telegraph  wire  having  a  circular  section  with  rapid 
currents,  has  more  than  three  times  the  virtual  resistance  during 
its  actual  work  than  that  supposed  to  be  its  true  resistance. 

The  self-induction  of  iron  diminishes  by  heating  the 
iron  or  by  putting  it  under  strain,  or  both.  A  moderate 
longitudinal  strain  decreases  its  self-induction  capacity  about 
40  per  cent.  Pass  a  constant  current  and  heat  an  iron  wire  to 
red  heat,  allowing  it  to  cool  with  the  current  on,  or  in  place  of 
heat  magnetize  the  wire,  or  in  place  of  magnetism  give  the  wire 
mechanical  vibrations;  the  result  of  either  step  is  a  strong 
internal  circular  magnetism,  so  that  a  wire  thus  treated  has 
no  longer  its  former  amount  of  self-induction,  which  has  fallen 
60  per  cent. 

A  bar  of  steel  having  north  and  south  magnetic-poles  may  be 
magnetized  so  that  there  will  be  a  weak  north  pole  at  the  south 
pole  and  a  weak  south  pole  at  the  north  pole.  This  is  called 
superimposed  magnetization. 

The  number  of  alternations  per  second  of  an  electric  current 
so  far  obtained  is  claimed  to  be  30,000. 

A  horizontally  pivoted  steel  magnet  or  needle  swings  in  a 
horizontal  plane  until  it  points  north;  and  a  vertically  pivoted 
magnetic  needle  dips  and  points  north,  the  earth  itself  being  a 
magnet. 

A  bar  of  iron  becomes  magnetic  when-  pointed  north,  but 
not  when  pointed  east  or  vertically;  the  magnetism  being,  how- 
ever, very  slight. 


119 

The  north  pole  of  a  magnet  continually  tends  to  attract  its 
south  pole.  The  center  of  the  magnet  neither  attracts  nor 
repels,  being  similar  in  this  respect  to  the  center  of  the 
earth. 

Some  mineral  compounds  of  iron  are  magnetic  and  some 
not.  Iron  pyrites  is  non-magnetic,  while  black  oxide  of 
iron  is  attracted  to  a  magnet.  In  both  cases  the  iron  is 
'chemically  combined  with  a  non-metal,  and  yet  they  possess 
opposite  properties;  again,  although  a  magnet  attracts  a  mag- 
netic substance  or  another  magnet,  magnetic  substances  will 
not  attract  each  other. 

A  compass  needle  points  at  a  slightly  different  angle  from 
year  to  year;  and  it' has  very  slight  daily  variations.  It  is  in- 
fluenced to  one  or  two  degrees  by  the  aurora  borealis.  In  the 
polar  regions  this  action  is  greatest,  and  occurs  also  before  the 
appearance  of  the  light. 

The  needle  generally  points  away  from  the  true  geographical 
pole  to  what  is  called  the  magnetic-pole.  It  would  be  found  to 
point  toward  the  geographical  pole  if  carried  on  the  following 
tour:  Commence  at  Philadelphia,  go  north  to  Hudson's  Bay; 
then  go  along  the  eastern  coast  of  the  White  Sea  and  across  the 
Caspian;  then  along  the  eastern  shore  of  Arabia,  through 
Australia,  to  the  South  Pole;  along  the  eastern  part  of  South 
America;  returning  to  Philadelphia. 

All  compass  needles  are  acted  upon  by  the  earth's  magnetism; 
but  by  attaching  two  parallel  needles  at  opposite  ends  of  a  stick 
in  such  a  manner  that  they  point  in  exactly  opposite  directions, 
the  action  of  the  earth  is  neutralized.  The  action  of  the  earth 
may  be  neutralized  also  by  a  large  permanent  magnet  at  such  a 
distance  from  the  needle  as  to  exactly  counteract  the  earth's 
magnetism.  In  either  of  the  above  cases  the  compass  will  be 
acted  upon  by  other  magnets  and  currents  the  same  as  if  no 
earth's  magnetism  existed.  Disturbances  in  the  sun  produce 
fluctuations  of  the  needle.  The  greatest  variation  ever  known 
was  noticed  a  few  hours  after  a  large  luminous  mass  was  seen  to 
pass  over  a  sun's  spot.  A  picture  of  the  magnetic  lines  of  force 
of  a  magnet  may  be  made  by  sprinkling  fine  iron  filings  on  a 
card  held  upon  the  poles  of  a  horseshoe  magnet.  The  lines 
are  all  curved  except  those  in  line  with  both  pole  centers.  Each 
filing  becomes  a  minute  magnet.  The  curves  are  closest 
together  at  the  poles,  spreading  as  they  radiate  therefrom.  The 
picture  is  made  permanent  by  first  waxing  the  paper  and  melt- 
ing the  wax  after  the  lines  are  formed.  While  forming,  the 
paper  should  be  slightly  shaken  to  assist  in  neutralizing  the 
friction.  A  compass  needle  at  any  position  lies  parallel  to  the 


120 

lines  of  force  represented  by  the  filings.  The  lines  of  force  are 
similar  to  the  rays  of  light,  in  that  the  more  lines  cut  by  a  sur- 
face the  greater  their  intensity  upon  that  surface,  while  an 
important  distinction  is  that  the  magnetic  lines  act  only  upon 
iron  and  slightly  on  only  a  few  other  substances.  A  bar  of  soft 
iron  which  has  become  a  feeble  magnet  by  holding  it  north  and 
south  (and  dipped  properly)  becomes  more  and  more  non- 
magnetic the  more  it  is  pointed  east  and  west.  Its  magnetism 
thus  obtained  may  be  made  permanent  by  twisting  or  hammer- 
ing. Steel  is  permanently  magnetized  by  peculiar  movements 
upon  a  second  magnet,  either  steel  or  electromagnetic.  The 
magnetism  is  much  stronger  and  more  permanent  if  heated  to 
212°  F.,  then  again  magnetized,  and  then  heated  as  before,  and 
so  on  for  six  times.  The  manner  of  magnetizing  is  to  move  one 
pole  of  the  magnetizing  magnet  back  and  forth  over  the  steel 
bar  to  be  magnetized.  A  better  way  is  to  move  different  poles 
of  two  strong  magnets  repeatedly  each  from  the  center  to  the 
opposite  ends  of  the  steel  bar  which  is  to  be  magnetized.  If 
this  steel  bar  joins  the  opposite  poles  of  a  third  and  fourth 
permanent  magnet,  the  said  bar  will  be  much  more  strongly 
magnetized.  The  higher  the  temper  of  steel,  the  more  difficult 
it  is  to  be  magnetized,  but  the  more  durable  is  its  magnetism. 
This  rule  is  true  only  for  steel  containing  equal  amounts  of 
carbon.  For  pieces  having  variable  amounts,  the  greatest 
magnetic  permanency  is  obtained  at  different  degrees  of 
temper.  It  is  a  peculiar  phenomenon  that  perfectly  pure  iron 
obtained  by  electroplating  has  the  property  of  becoming 
slightly  permanently  magnetized,  showing  that  this  property  is 
not  absolutely  due  to  the  carbon  in  steel;  especially  does  it  not 
appear  to  be  due  to  the  carbon  when  it  is  remembered  that  cast 
iron  contains  more  carbon  than  steel  and  yet  is  practically 
non-susceptible  to  being  permanently  magnetized.  Incandescent 
and  even  red-hot  iron  are  not  attracted  by  a  magnet;  and  a 
permanent  steel  magnet  loses  its  magnetism  at  bright  red  and 
is  not  attracted  by  a  magnet.  A  steel  magnet  which  has  been 
heated  is  weaker  when  cooled  than  before.  When  cooled  from 
red  heat,  its  magnetic  force  is  substantially  zero.  If,  at  the 
same  time  a  bar  of  steel  is  being  magnetized,  it  is  hammered  or 
twisted,  it  will  acquire  a  higher  degree  of  magnetism.  The 
falling  of  a  steel  magnet  after  magnetization  weakens  it.  In  short, 
twisting  or  hammering  after  magnetization  weakens  the  magnet. 
Twisting  repeatedly  in  the  same  direction  does  not  repeat  the 
weakening,  but  subsequent  twisting  in  an  opposite  direction 
diminishes  the  magnetic  force.  Magnetization  of  iron  wires 
diminishes  the  twisting  power  thereof.  Pass  sewing  needles 


121  ,    , 

through  very  small  corks  and  float  them  on  water.  Bring  a 
magnet  near  the  same.  The  corks  arrange  themselves  in 
geometrical  figures,  whose  shape  depends  upon  the  number  of 
corks.  A  slight  motion  of  the  water  will  often  cause  the  corks 
to  rearrange  themselves  in  differently  relative  positions.  Finally 
a  figure  will  be  obtained  which  will  be  staple. 

Generally  it  may  be  said  that  magnets  act  only  upon  iron, 
nickel  considerably,  and  two  or  three  other  metals  very  slightly; 
but  there  are  exceptions,  or  rather  magnets  act  upon  nearly  all 
substances,  but  in  a  different  manner.  A  gas  may'  be  repelled 
by  a  magnet;  thus  let  a  candle-flame  be  used  as  it  is  visible  gas; 
place  the  candle  so  that  its  flame  is  between  the  poles  of  a 
powerful  magnet.  The  flame  is  repelled.  Other  illustrations  in 
the  case  of  gas  are  as  follows:  Place  a  small  piece  of  iodine  on 
a  plate  between  the  poles  and  apply  heat.  The  colored  vapor 
is  seen  to  be  deflected  by  the  magnet  as  if  by  a  breeze.  The 
gas  which  is  acted  upon  most  powerfully  is  oxygen  gas,  but 
being  colorless,  the  fact  is  difficult  of  exhibition.  One  of  the 
best  ways  is  to  make  soap  bubbles  with  any  given  gas  and  place 
the  bubbles  near  the  poles.  Liquids  are  also  acted  upon,  Fill 
closed  tubes,  each  with  a  different  liquid,  and  suspend  in  a 
horizontal  position  by  a  silk  thread.  The  tubes  will  assume  a 
fixed  position.  With  ether,  alcohol,  milk,  water  or  blood  the 
tube  will  stand  at  right  angles  to  the  axes  of  the  pole-pieces; 
if  of  solutions  of  the  compounds  of  iron  or  cobalt,  the  tubes 
will  stand  parallel  to  said  axes.  As  to  solids,  a  piece  of  cop- 
per suspended  by  a  silk  thread  between  the  poles  and  rotated 
is  stopped  almost  instantly  by  the  magnetism.  Other  substances 
acted  upon,  especially  if  in  the  form  of  rods  or  bars,  are  bread, 
sugar,  sulphur,  alum,  iodine,  phosphorus,  glass  and  rock  crystal. 
It  is  thought  that  all  substances  are  either  repelled  or  attracted 
by  magnets,  provided  the  same  are  sufficiently  powerful. 

A  most  remarkable  phenomenon  is  that  accompanying  a 
spark  formed  between  the  poles  of  a  powerful  magnet.  Let 
the  terminals  of  the  circuit  of  the  magnet  touch  at  a  point  be- 
tween the  two  poles.  A  sound  like  that  of  a  pistol  is  produced. 
When  a  fine  wire  of  tin,  zinc,  bismuth  or  iron  under  tension 
conducts  an  intermittent  current,  the  wire  produces  a  sound  at 
each  break  of  the  circuit. 

Magnets  are  generally  rigid  and  the  poles  at  fixed  distances 
from  each  other.  If  the  magnet  is  straight,  the  poles  are  at  a 
maximum  distance  and  have  the  maximum  power.  When  the 
distance  is  zero,  the  magnetism  is  not  zero,  but  is  at  its  mini- 
mum; as  is  illustrated  by  connecting  the  poles  of  a  horseshoe 
magnet  by  a  piece  of  soft  iron.  Other  pieces  will  still  be 


122 

attracted,  but  not  with  such  force  as  when  the  poles  are  not 
connected  by  iron.  If  connected  by  other  metal,  except  nickel, 
the  magnetism  is  not  appreciably  diminished.  If  the  magnet  is 
flexible,  torsional,  compressible  or  extensible,  and  the  poles  are 
within  the  proper  distance,  they  will  move  one  way  or  another, 
the  movement  being  due  to  an  attractive  force  between  the 
poles.  A  magnet  for  any  given  strength  must  be  wound  accord- 
ingly. If  for  a  current  having  a  high  electromotive  force,  the 
coil  should  be  made  of  a  long,  fine  wire;  if  the  current  is  one 
of  low  pressure,  the  wire  should  be  of  large  diameter  and 
comparatively  short.  When  sugar  is  added  to  water  it  dissolves; 
but  soon  the  degree  of  saturation  is  reached  at  which  no  more 
sugar  will  dissolve.  So  also  with  a  magnet.  Begin  with  a 
small  current  and  increase  it.  The  magnet  becomes  stronger 
and  stronger,  but  soon  becomes  no  stronger,  although  the 
current  continues  to  increase.  A  'magnetic  force  is  the  most 
steady  for  any  given  fluctuating  current,  when  the  convolutions 
of  wire  are  more  and  more  numerous  from  the  ends  toward 
the  center.  There  are  different  ways  in  which  water  may  be 
made  to  dissolve  a  solid  above  its  normal  degree  of  saturation; 
for  example,  the  water  may  be  heated.  In  the  case  of  a  mag- 
net more  effective  magnetism  per  unit  of  current  is  obtained  if 
the  iron  core  is  made  of  insulated  iron  plates  or  wires.  Again, 
the  magnet  will  reach  its  point  of  saturation  quicker  with  a 
solid  than  with  a  porous  iron  core.  Below  the  point  of  satura- 
tion the  magnetism  varies  with  the  current  in  the  most  economical 
proportion  if  the  core  is  from  three  to  four  times  the  diameter. 
Since  the  breaking  of  a  current  causes  a  sound  in  the  iron  of 
a  magnet  (the  iron  being  suitably  suspended  and  resting  against 
a  sounding-board  and  the  iron  being  alternately  expanded  and 
contracted),  it  is  natural  to  infer  that  if  iron  is  alternately  ex- 
panded and  contracted  (e.  g.,  by  heat  and  cold)  by  any  suitable 
means,  it  will  become  magnetic.  Such  is  the  case,  but  the 
magnetism  is  very  slight.  When  a  stone  is  lifted  from  the 
ground  mechanical  energy  is  stored ;  because  the  stone  in 
falling  can  perform  the  same  work  (as  in  driving  a  clock)  as  was 
required  to  lift  it.  So  also  is  it  the  case  with  a  small  piece  of 
iron  pulled  away  from  a  magnet.  It  requires  a  force  to  pull  it 
away.  Work  is  done.  Of  two  pieces  of  iron  and  steel  of  the 
same  weight,  the  one  is  more  attracted  than  the  other  by  a 
given  magnet.  The  shorter  a  magnet,  the  more  quickly  it  is 
magnetized  when  the  circuit  is  closed,  and  the  more  quickly  it 
is  demagnetized  when  the  circuit  is  interrupted.  Let  a  magnet 
be  a  long  magnet.  A  piece  of  iron  is  attracted  with  greater 
force  in  the  direction  of  the  major  than  of  the  minor  axis.  A 


123 

piece  of  iron  which  has  never  been  magnetized  is  more  sensitive 
than  one  of  the  same  weight  and  size  which  has  been  mag- 
netized; but  its  original  condition  may  be  obtained  by  reversing 
the  current.  An  armature  may  be  removed  from  a  magnet  by 
external  force;  but  also  by  heating  the  magnet  or  armature  or 
both.  There  is  no  difference  in  the  natures  of  a  permanent 
magnet  and  electromagnet;  but  there  are  certain  characteristic 
differences.  The  former  cannot  be  demagnetized  and  magnet- 
ized simply  by  respectively  closing  and  opening  an  electric 
circuit,  or  varied  in  strength  simply  by  varying  the  strength  of 
the  current.  If  a  piece  of  steel  is  employed  as  the  core  of  a 
magnet,  the  magnetism  cannot  be  varied  from  zero  to  maximum, 
as  can  be  approximately  done  with  soft  iron  as  a  core.  The 
friction  of  iron  sliding  upon  iron  may  be  varied  by  variation  of 
a  current,  carried  by  a  wire  wound  upon  the  iron. 

By  varying  the  length  of  a  magnet  its  magnetism  is  varied. 
If  two  magnets  are  in  branch  circuits,  an  increase  of  resistance 
in  either  branch  will  increase  the  magnetism  of  the  magnet  in 
the  other  branch.  It  is  like  two  rivers  branching  away  from 
each  other  and  meeting  again.  Dam  or  partially  dam  up  one 
branch  and  more  water  will  flow  through  the  other  branch. 
Magnetism  is  diminished  and  almost  extinguished  by  joining 
the  ends  of  the  coil  by  a  wire  of  large  size.  The  degree  of 
saturation  of  a  piece  of  steel  is  increased  by  adding  to  it  in  the 
process  of  manufacture  about  4  per  cent,  of  the  element 
tungsten.  The  magnetism  is  also  more  permanent.  If  any 
given  movement  of  a  bar  of  steel  before  a  magnet  magnetizes 
the  steel,  the  reverse  movements  will  almost  demagnetize  it. 

Motion  between  two  magnets  may  be  obtained  with  an 
alternating  current  by  placing  the  magnets, in  series  with  each 
other.  When  either  pole  changes  its  polarity,  the  other  does 
also,  and  consequently  the  force  exerted  by  one  magnet  upon 
the  other  is  constant  as  far  as  the  senses  are  concerned;  but 
analytically  considered,  the  force  is  rapidly  intermittent. 

When  an  alternating  current  is  passed  through  an  ordinary 
magnet,  especially  if  having  a  great  many  windings,  the  current 
is  greatly  diminished;  but  not  with  the  same  results  as  obtained 
when  passed  through  a  rheostat  or  similar  resistance.  In  the 
latter  case  the  current  is  lost  in  the  form  of  heat;  but  in  the 
former  only  a  very  small  portion  of  that  which  disappears  is 
lost.  This  is  why  a  magnet  so  used  is  called  a  choking  magnet. 
It  serves  to  stop  a  part  of  the  current  by  stopping  partially  the 
generation.  A  choking  magnet  may  be  more  or  less  deprived 
of  this  property  by  placing  it  inside  of  a  ring  of  metal  of 
considerable  mass.  The  current  is  then  hindered  but  very 


124 

slightly.  It  is  found  that  it  is  difficult  to  move  the  magnet 
through  the  ring,  and  also  that  if  the  magnet  is  fixed,  the 
ring  will  be  repelled  from  the  center  of  the  magnet. 

If  a  copper  disc  is  delicately  suspended  or  balanced  horizon- 
tally above  the  end  of  a  vertical  magnet,  it  is  repelled  by  an 
intermittent  current.  Currents  are  induced  in  the  disc  which  is 
consequently  repelled.  An  alternating  current  may  be  substituted 
for  the  intermittent  with  similar  effects.  It  is  found  that  an 
induced  current  in  a  secondary  conductor  is  a  little  behind 
time  with  respect  to  an  inducing  current.  Consequently,  when 
any  given  induced  impluse  is  just  about  to  cease,  an  inducing 
impluse  is  beginning.  Consequently,  replusion  takes  place. 

The  disc  and  ring  are  equivalents  in  that  the  latter  may  be 
considered  as  composed  of  concentric  rings.  If  the  disc  is 
placed  between  the  magnet  and  the  ring,  the  latter  is  not 
repelled,  although  it  is  strongly  repelled  more  and  more  while 
the  disc  is  being  removed.  If  the  ring  is  replaced  by  a  coil  in 
circuit  with  an  incandescent  lamp,  the  same  is  extinguished  or 
lighted  according  as  to  whether  the  disc  is  or  is  not  between  the 
coil  and  the  magnet. 

If  the  coil  and  lamp  are  balanced  above  the  magnet,  the 
primary  current  may  fluctuate  between  considerable  limits  and 
yet  the  intensity  of  the  light  will  remain  constant. 

If  two  rings  are  placed  over  the  alternating  current  magnet, 
it  will  be  found  difficult  to  slide  one  ring  from  the  other,  and 
when  let  go,  they  will  attract  each  other  until  they  are  concen- 
tric rings. 

If  the  disc  is  pivoted  at  its  center  eccentrically  to  the 
magnet,  it  will  rotate  when  the  ring  is  held  parallel  to  the  disc. 
It  is  due  to  the  attractive  action  between  the  disc  and  ring. 

The  action  of  repulsion  between  the  magnet  and  ring  or 
disc  is  called  by  different  names — hysteresis,  magnetic  friction 
and  magnetic  lag.  Whatever  the  name,  the  principle  is  the 
same,  being  the  motion  due  to  the  primary  impluses  of  one 
direction  upon  the  retarded  induced  impulses  of  the  opposite 
direction.  When  two  rings  are  used  as  described,  they  have 
induced  currents  both  obtained  from  the  magnet,  and  conse- 
quently the  induced  currents  are  both  alike  in  the  same  direction, 
and  consequently  attraction  takes  place. 

A  copper  ball  rotates  if  placed  upon  the  disc  which  rests 
horizontally  upon  the  end  of  the  alternating  current  magnet. 

In  general,  an  alternating  current  magnet  acting  upon  a 
closed  conductor  produces  repulsive  motion,  which  may  by 
proper  mechanism  or  relative  disposition  be  rotary,  recipro- 
cating, &c. 


125 

A  bar  made  of  two  strips  of  different  metals  bends  when 
heated  by  atmospheric  changes  of  temperature  or  by  an  elec- 
tric current  or  other  source  of  heat.  A  bar  of  two  strips  of  the 
same  metal,  and  having  different  amounts  of  radiating  surfaces 
and  different  resistances,  and  electrically  insulated  from  each 
other,  does  not  bend  by  changes  of  atmospheric  temperature, 
but  does  bend  by  the  heat  developed  during  the  passage  of  an 
electric  current,  whether  continuous,  intermittent  or  alternating. 

The  space  immediately  surrounding  a  wire  carrying  a  con- 
tinuous and  uniform  current  contains  what  may  be  termed 
static  or,  better,  stored-up  energy.  A  second  wire  parallel  to 
the  first  will  receive  no  current  during  the  existence  of  the 
continuous  uniform  current,  because  the  field  of  force,  or  the 
space  containing  the  stored  electric  energy,  corresponds  to  air 
held  under  pressure  by  an  excessive  weight.  Take  the  weight 
away,  and  the  air  will  expand  and  produce  work.  Similarly  inter- 
rupt the  uniform  continuous  current.  This  corresponds  to 
removing  the  weight.  Immediately  a  current  is  found  in  the 
second  wire,  lasting  until  the  first  current  has  diminished  to 
zero.  If  the  weight  is  partially  lifted,  the  expanding  air  will 
perform  work;  so  also  will  a  current  appear  in  the  second  wire 
during  the  time  that  a  resistance  is  introduced  into  the  first 
wire  circuit.  Similarly,  as  any  decrease  or  increase  of  the 
weight  will  vary  momentarily  the  amount  of  work  done  by  the 
compressed  air,  so  will  any  variation  of  the  current  in  the  first 
wire  produce  a  current  in  the  second  wire.  Again,  as  long  as 
the  current  in  the  first  wire  is  constant,  no  current  will  appear 
in  the  second  wire.  In  the  above  cases  the  second  wire  is 
supposed  to  be  closed  upon  itself  like  a  ring.  If  it  is  an  open 
circuit,  it  will  receive  a  static  charge  in  the  place  of  a  current 
at  each  variation  of  the  current  in  the  first  wire.  The  effects 
of  the  field  of  force  around  the  first  wire  depends  upon  the 
medium  which  surrounds  it.  If  iron  is  used,  the  currents  in 
the  second  wire  are  greater  than  without  it;  not  that  there  is 
any  force  generated,  but  less  becomes  useless  by  dissipation. 
The  iron  surrounding  the  wire  acts  as  a  concentrator  of  the 
field  of  force.  The  iron  should  for  best  effects  consist  of 
laminae  insulated  from  one  another  and  lying  in  planes  per- 
pendicular to  the  axis  of  the  wire,  or  else  should  be  an  in- 
sulated iron  wire  wound  helically  about  the  wires.  The 
presence  and  effect  of  the  iron  about  the  wires  may  be  com- 
pared to  substituting  the  good  conductor  copper  for  carbon  in 
an  electric  circuit.  The  iron  is  the  best  conductor  of  the 
magnetic  currents  forming  the  field  of  force  around  the 
conductors.  These  magnetic  currents  are  in  concentric  circles 


around  the  axis  of  the  first  conductor.  The  reason  of  lamina- 
ting an  iron  core  may  now  be  apparent.  If  not  laminated,  a 
static  charge  occurs  upon  the  iron  in  a  longitudinal  direction, 
which  is  discharged  as  a  current  at  each  variation  of  primary 
current.  This  current  in  the  iron  circulates  longitudinally 
from  one  part  of  the  iron  to  another.  This  can  be  more  easily 
appreciated  by  considering  that  the  iron  which  surrounds  the 
wires  is  a  tube  slipped  over  the  same,  and  several  feet  thick. 
Or  more  forcibly  by  supposing  the  wires  are  rings  and  the  iron 
is  a  tube  whose  ends  are  in  contact.  The  iron  would  then  act 
not  only  as  a  conductor  of  the  currents  in  the  field  of  force, 
but  also  as  a  secondary  conductor.  Practice  shows  this  to  be  so, 
because  such  a  tubular  core  becomes  very  hot  on  account  of 
the  currents  which  are  called  Foucault  currents.  By  lamina- 
ting the  core  no  longitudinal  currents  can  be  conducted  by  the 
iron  to  a  greater  distance  than  the  thickness  of  each  lamina. 

A  converter  for  intermittent  currents  should  have  an  open 
magnetic  core;  while  for  alternating  currents  the  core  should  be 
closed  upon  itself,  unless  the  alternations  are  unusually  slow. 
It  is  peculiar,  though  not  difficult  to  understand,  that,  while  the 
impulses  of  an  intermittent  current  are  all  of  one  direction,  yet 
the  induced  impulses  of  current  formed  in  an  adjacent  closed 
secondary  conductor  are  alternating  in  direction.  The  analysis 
of  the  action  is  thus:  When  an  impluse  of  the  intermittent  cur- 
rent begins  it  must  increase  from  zero  to  maximum,  thereby 
inducing  a  current  having  a  different  direction  from  that  which 
will  be  produced  when  the  said  impulse  stops,  /'.  e.,  decreases 
from  maximum  to  zero;  all  depending  upon  the  principle  that 
increasing  and  decreasing  currents  induce  currents  of  opposite 
direction  in  a  secondary  conductor. 

A  current  of  electricity  in  a  wire  has  often  been  compared 
to  a  current  of  water  in  a  tube;  but  in  the  one  case  the  water 
is  confined  within  the  tube  while  in  the  other  the  electric  cur- 
rent is  not  only  in  the  wire,  but  also  in  the  space  surrounding 
the  wire.  Practically,  this  space  is  comparatively  slight,  being 
possible  of  detection  for  only  a  few  feet  with  the  highest  elec- 
tromotive force  currents,  but  theoretically  it  extends  to  an 
infinite  distance. 

If  a  wire  carrying  a  current  is  wound  upon  glass,  the  mole- 
cules of  the  latter  undergo  a  new  motion  from  that  due  to  the 
ordinary  heat  vibrations.  The  new  motions  are  detectible  by 
polarized  light. 

The  greater  the  rate  of  vibration,  alternation,  intermission, 
undulation  or  other  oscillation  of  a  current  in  a  wire,  the  larger 
the  proportion  of  current  found  upon  the  surface  and  in  the 


127 

space  surrounding  the  wire.  In  electric  lighting  systems  the 
same  are  much  more  efficient  if  the  single  conductor  is  replaced 
by  several  small  conductors,  or  by  a  single  tape  conductor  so 
as  to  obtain  more  surface  per  mass. 

When  a  continuous-current  circuit  is  closed  or  broken, 
some  substance  in  space  surrounding  the  conductor  is  set  into 
vibration.  These  vibrations  stop  as  soon  as  the  current  is 
uniformly  continuous,  but  the  assumed  unknown  substance 
(thought  to  be  the  same  which  propagates  light  vibrations) 
continues  to  be  held  in  an  altered  condition  from  that  before 
the  circuit  is  broken  or  closed  respectively. 

A  proof  of  the  latter  part  of  the  statement  above  becomes 
apparent  by  holding  a  compass  needle  over  the  conductor.  It 
is  deflected  until  it  stands  at  right  angles  to  the  wire. 

Electricity  is  generally  converted  into  mechanical  motion  by 
a  magnet;  but  this  is  not  the  only  way.  Take  a  horizontal  tube, 
whose  ends  are  bent  upwards.  Fill  with  a  conducting  liquid 
like  salt  water  or  dilute  sulphuric  acid.  Drop  in  a  globule  of 
mercury.  Pass  a  current  through  the  liquid.  The  mercury 
travels  from  one  end  of  the  tube  to  the  other  in  a  direction 
dependent  upon  that  of  the  current.  It  moves  with  sufficient 
force  to  make  it  travel  up  hill,  and  moves  with  greater  and 
greater  force  as  the  current  is  greater  and  greater.  A  liquid 
may  be  raised  above  its  natural  level  by  the  direct  action  of  the 
current.  Divide  a  porous  jar  into  two  compartments  by  a  porous 
partition  and  introduce  a  decomposable  liquid,  conveniently, 
cupric  sulphate  dissolved  in  water.  Introduce  electrodes  and 
pass  a  current  from  one  liquid  to  the  other.  A  difference  in  the 
heights  of  the  liquids  occurs.  The  converse  of  the  above 
phenomenon  is  also  true.  If  a  liquid  is  forced  through  a 
diaphragm  from  an  enclosed  compartment,  a  current  in  the 
direction  of  the  motion  of  the  liquid  is  produced,  and  the  elec- 
tromotive force  increases  with  the  pressure.  Whenever  a  liquid 
in  a  vessel  is  stirred,  a  current  is  produced.  The  liquid  in  the 
interior  of  the  earth  is  always  in  motion  and  the  earth  currents 
may  probably  be  explained  on  this  principle.  Molecules  are 
set  into  motion  by  the  current.  This  is  illustrated  by  the  arc 
lamp  in  which  particles  of  carbon  are  carried  from  the  positive 
electrode  to  the  negative.  A  piece  of  iron  gives  forth  a  sound 
when  magnetized  by  a  vibrating  current,  being  due  to  the  mechan- 
ical motions,  compressions  and  expansions,  which  are  communi- 
cated to  the  air.  A  vibratory  motion  may  be  communicated  to 
a  globule  of  mercury  in  substantially  the  following  manner: 
Take  a  vessel  of  dilute  sulphuric  acid  containing  a  very  small 
proportion  of  chromic  acid,  and  place  therein  a  globule  of 


128 

mercury.  Immerse  an  iron  wire  until  it  just  touches  the 
mercury.  The  globule  of  mercury  will  vibrate  and  will  con- 
tinue to  do  so  indefinitely.  The  mercury  vibrates  in  a  very 
regular  manner.  By  close  observation,  the  vibrations  are  seen 
to  consist  of  elongations  and  contractions.  It  is  first  spherical, 
and  then  egg-shaped,  and  so  on. 

An  English  electrical  paper  contains  the  following  novel 
article  by  Dr.  Mengarini  : 

"  If  a  platinum  and  acidulated  water  voltameter  is  traversed 
by  an  alternating  current,  which,  by  means  of  an  adjustable 
resistance,  can  be  kept  at  a  constant  value  whilst  the  surface  of 
one  of  the  electrodes  is  gradually  diminished,  a  point  is  reached 
at  which  the  current  density  at  the  movable  electrode  becomes 
so  great  that  large  bubbles  of  gas  are  evolved  which  for  a 
moment  insulate  a  portion  of  the  electrode  from  the  liquid.  The 
metallic  surface  is  then  capable  of  igniting  the  bubbles  of  gas, 
producing  small  explosions  and  flashes  of  light  in  the  liquid. 
With  care  it  is  possible  to  render  the  electrode  incandescent 
along  its  whole  length,  so  that  it  is  covered  with  a  sheet  of 
flame  from  which  dart  flashes  of  bluish  light  with  little  ex- 
plosions. At  the  same  time  on  the  first  electrode,  where  the 
current  density  has  remained  constant,  appears  a  copious  evolu- 
tion of  gas,  without  comparison  greater  than  it  was  at  first  when 
the  other  electrode  did  not  exhibit  this  phenomenon  of  recombi- 
nation. This  gas  is  found  to  be  a  mixture  very  rich  in  hydrogen. 
If  it  is  a  salt  that  is  being  decomposed,  a  considerable  deposit  of 
metal  takes  place  on  the  second  electrode,  which  is  seen  by 
simple  inspection,  without  the  necessity  of  weighing,  to  be  very 
much  greater  than  that  which  would  have  taken  place  under 
ordinary  conditions.  If  on  the  electrode  whose  surface  has  been 
kept  constant,  the  current  density  is  so  small  that  no  trace  of 
decomposition  appears  on  it;  still,  as  soon  as  the  first  electrode 
commences  to  be  incandescent,  the  products  of  decomposition 
immediately  appear  on  the  second,  which,  in  the  case  of  solid 
ions,  at  once  becomes  covered  with  a  metallic  deposit,  just  as  if  it 
formedthe  negative  electrode  of  a  voltameter  traversed  by  a  direct 
current.  A  similar  result  occurs  if  one  of  the  electrodes,  without 
being  covered  by  a  sheet  of  gas  from  which  starts  a  continuous 
series  of  explosions,  is  surrounded  by  liquid  in  a  state  of  strong 
ebullition,  so  that,  without  any  luminous  phenomena,  the  elec- 
trode gives  out  a  feeble  sound,  resembling  the  hum  of  a  gnat. 
In  order  to  carry  out  this  experiment,  it  is  sufficient  to  enclose 
the  electrode  in  a  porous  cell  immersed  in  the  liquid.  After 
starting  the  current,  as  soon  as  the  density  reaches  a  suitable 
value,  the  liquid  enters  into  ebullition.  If  a  third  electrode  of 


129 

platinum  is  placed  in  the  voltameter  containing  the  two  elec- 
trodes when  the  above  experiments  are  being  made  and  a  wire 
carried  from  it  to  one  terminal  of  a  galvanometer,  the  other 
terminal  of  which  can  be  connected  by  means  of  a  key  to  either 
of  the  two  original  electrodes,  it  is  found,  on  suddenly  breaking 
the  alternating  circuit,  that,  whilst  the  electrode  that  became 
incandescent  is  either  not  polarized  at  all,  or  only  very  feebly 
so,  that  with  the  larger  surface  shows  strong  polarization,  the 
direction  of  the  current  being  the  same  as  that  from  the  copper 
pole  of  a  volta  couple.  On  inserting  other  voltameters  con- 
taining sulphate  of  copper,  nitrate  of  silver,  etc.,  in  series  with 
the  first  and  placing  therein  electrodes  of  such  an  area  that 
decomposition  does  not  occur  when  the  alternating  current 
passes  through  them,  as  soon  as  the  above  phenomenon  takes 
place,  the  current  remaining  constant,  an  active  electrolytic 
decomposition  commences  with  deposition  of  copper,  silver, 
etc.,  in  each  of  the  other  voltameters." 

Hurmuzescu  states  in  the  Electrical  Review  (London)  the 
following: 

"  A  fine  wire  stretched  between  two  supports,  one  of  which 
is  provided  with  a  strainer  or  spring,  for  regulating  the  tension, 
on  being  traversed  by  a  large  continuous  current  begins  to  vi- 
brate  The  explanation  of  this  fact  seems 

to  me  to  lie  in  the  interchange  of  heat  between  the  wire  and 
the  surrounding  atmosphere;  this  constitutes  really  a  thermic 
motor,  in  which  the  energy  expended  is  supplied  by  the 
current." 


CHAPTER  XIV. 
"  I'VE    GOT    AN    IDEA." 

THIS  is  the  exclamation  which  usually  heralds  the  embryo  of 
an  invention.  It  has  been  uttered  so  often  as  to  become  a 
familiar  expression.  As  soon  as  such  an  announcement  is  made 
the  inventor  knows  that  it  is  only  a  matter  of  intelligence, 
knowledge,  work  and  practice  to  develop  the  idea  into  a  clear 
conception,  and  the  conception  into  a  complete  invention 
When  he  arrives  at  the  stage  of  being  able  to  say  :  lye  got 
an  idea,"  he  has,  substantially,  the  invention.  He  has  obtamec 
that  which  he  has  sought.  He  seems  enthusiastic.  He  make! 
sketches  mentally  and  on  paper  of  a  device  which  will  carry  out 


130 

his  idea.  He  obtains  all  the  knowledge  he  possibly  can  which 
will  assist  him  in  developing  the  invention.  He  realizes  the  im- 
portance of  practice  in  development  and  of  knowing  how  earlier 
inventors  made  the  quickest  progress  in  development.  He  feels 
that  the  import  of  the  conception  is  so  great  that  he  cannot  know 
too  much  of  that  which  he  feels  every  inventor  is  supposed  to 
know.  He  is  like  a  man  who  starts  a  new  business  with  which  he 
is  not  acquainted;  each  day  shows  him  his  ignorance  of  what  he 
ought  to  have  known.  He  realizes  the  importance  of  preliminary 
preparation. 

What  great  benefits  and  wealth  have  resulted  from  such  ideas! 
How  many  luxuries  and  conveniences  have  grown  therefrom! 
Such  ideas  have  singly  been  the  foundation  of  a  fortune.  What 
physical  objects  of  property  have  outweighed  in  value  mental 
acts  called  an  idea  ?  Therefore,  is  it  not  important  to  inves- 
tigate the  causes  of  ideas,  learn  if  an  idea  is  simple  or  compound, 
and  if  compound,  to  discover  its  element  by  a  process  of 
analysis  ?  If  this  can  be  done,  how  important  it  will  be  to  a 
would-be  inventor  ?  If  an  idea  is  something  which  is  obtainable 
by  money,  work,  knowledge,  or  any  other  form  of  acquirable 
property,  the  inventor  may  be  assumed  to  be  anxious  to  know 
the  fact.  The  popular  mind  apparently  seems  to  look  upon  an 
idea  as  something  which  has  been  bestowed  upon  a  person  by 
some  power  independent  of  any  action  on  his  part  further 
than  the  passive  action  of  reception  of  an  idea.  The  very  ex- 
pression forming  the  title  of  this  chapter  contradicts  such  a 
notion.  The  inventor  says:  "  I've  got  an  idea,"  or  "Eureka, "• 
meaning  "  I've  found  it."  To  get  a  thing  implies  action.  To  find 
a  thing  implies  action.  Again,  it  will  probably  be  found  by 
investigation  that  an  idea  is  not  a  myth,  but  it  is  something. 
Chemical  compounds  are  made  by  putting  two  or  more  elements 
together.  If  ideas  are  compound,  much  light  will  be  obtained 
and  much  assistance  arrived  at  if  the  compound  idea  can  be 
analyzed.  The  problem  before  us  is  evidently  a  great  one;  it 
is  of  so  much  importance  that  an  attempt  to  solve  it  cannot  be 
spent  in  vain,  even  if  only  one  ray  of  light  is  caused  to  enlighten 
the  beginning  of  the  road  leading  to  its  solution. 

The  problem  is  resolved  into  parts  represented  by  the  fol- 
lowing questions:  Is  an  idea  single  or  compound  ?  If  com- 
pound, what  are  its  elements  ?  How  can  an  idea  be  obtained  ? 
What  other  useful  data  can  be  obtained  by  investigation  ?  The 
answers  are  most  probably  found  hidden  in  examples  of  the 
past.  The  astronomer  can  predict  eclipses  because  he  studies 
the  causes  of  former  eclipses.  The  geologist  can  give  informa- 
tion of  the  existence  of  certain  substances  under  the  surface  of 


131 

any  given  portion  of  the  earth  without  seeing  those  substances, 
because  he  knows  general  principles  and  laws  pertaining  to  the 
fixed  relations  of  the  visible  to  the  invisible  constituents  of  the 
earth  at  other  portions  of  its  surface.  Similarly,  it  may  become 
possible  to  learn  how  to  get  an  idea  as  a  basis  of  an  important 
invention,  if  past  ideas  be  carefully  studied,  and,  if  compound, 
analyzed.  The  invention  of  printing  is  taken  first  as  a  basis  for 
study. 

Coster  was  the  first  to  conceive  the  idea  of  replacing  hand- 
writing by  printing.  He  had  often  thought  what  a  blessing  it 
would  be  to  the  people  at  large  to  be  able  to  own  books,  which 
at  that  time  were  very  expensive  because  multiplication  was  done 
by  hand.  Only  rich  people  owned  them.  When  he  became  old, 
he  was  in  the  habit  of  strolling  into  the  woods,  and  upon  one 
occasion  found  the  initials  of  his  fiancee,  which  he  had  carved 
upon  the  bark  of  a  tree  when  a  young  man.  This  led  him  to 
cut  off  bark  and  cut  it  into  letters,  which  he  naturally  took  home, 
and  finding  that  his  grandchildren  liked  to  play  with  them, 
he  carved  many  letters  and  used  the  same  as  means  for  teach- 
ing the  children  to  read.  On  one  occasion  he  brought  home 
the  letters  wrapped  up  snugly  in  a  piece  of  parchment.  Some 
of  them  remained  stuck  to  the  parchment,  and  after  removal  by 
one  of  the  children,  imprints  were  left  upon  the  surface  and 
attracted  the  attention  of  one  of  the  boys,  who  showed  them  to 
his  grandfather.  The  latter  was  struck  with  the  incident  as  a 
wonderful  phenomenon,  and  studied  into  the  cause  in  a  severely 
critical  and  analytical  manner.  He  found  that  the  pressure 
upon  the  letters  had  squeezed  out  some  of  the  colored  sap,  which 
stuck  to  the  parchment  at  all  points  of  contact  of  the  same  with 
the  letters.  Was  this  an  invention  ?  No.  He  no  more  had  an 
invention  than  the  boy  who  first  saw  the  prints.  He  had  already 
done  more  than  the  boy.  The  latter  saw  the  prints,  enjoyed  the 
phenomenon.  Coster  did  more.  He  sought  the  cause.  When 
he  knew  the  cause,  he  learned  something  he  never  knew  before. 
He  learned  a  fact  that  a  bark  letter  containing  moist  sap  pressed 
upon  a  surface  of  parchment  paper  left  an  imprint.  This  was 
knowledge,  not  an  invention.  He  had  been  for  a  long  time  try- 
ing to  solve  the  problem  of  multiplication  of  letters  and  words 
upon  parchment.  His  idea  consisted  in  putting  this  and  that 
together.  His  idea  was  compound.  It  consisted  of  two  ele- 
mentary constituents,  by  whatever  name  the  constituents  may  be 
called.  The  two  constituents  were  two  facts,  namely  :  (a)  A 
moist  letter  leaves  an  imprint  upon  parchment  as  often  as  it  is 
pressed  thereon.  (£)  Duplicating  books  by  hand  is  a  very  slow 
and  expensive  process.  He  put  these  two  facts  together  and 


132 

was  able  to  say:  I've  got  an  idea.  He  might  have  continued 
to  leave  either  fact  by  itself  for  the  rest  of  his  life  without  making 
an  invention.  He  had  as  a  very  prominent  part  of  his  knowledge 
the  fact  that  books  were  made  by  a  very  slow  and  expensive 
process,  and  had  been  seeking  for  that  knowledge  by  which  he 
could  remove  the  difficulty.  When  he  obtained  the  other  fact 
or  element,  it  is  easier  to  comprehend  the  naturalness  of  his 
putting  the  two  facts  together  than  of  leaving  them  alone  and 
separated.  This  principle  of  the  action  of  the  mind  is  illustrated 
by  other  examples  If  a  person  is  intensely  striving  to  solve  a 
given  problem,  it  is  natural  for  him  to  apply  knowledge  almost 
as  soon  as  it  becomes  a  part  of  his  education.  I  admit  that  it 
is  useless  to  try  to  explain  the  nature  of  the  power  which 
prompted  him  to  put  the  two  facts  together;  just  as  it  is  im- 
possible at  present  for  physicists  to  explain  the  inherent  nature 
of  that  wonderful  force  which  at  a  distance  of  millions  of  miles 
holds  the  planets  and  stars  in  their  places;  or  that  force  by  which 
hydrogen  and  oxygen  unite  and  form  water,  which  differs  in 
every  respect  from  the  hydrogen  and  oxygen  when  simply  mixed; 
or  that  force  which  holds  a  pith-ball  to  a  piece  of  amber  which 
has  been  rubbed;  or  that  force  which  lights  up  the  world  day 
after  day  for  years  and  years.  Although  the  nature  of  these 
forces  cannot  be  understood,  yet  they  are  just  as  useful  to  man- 
kind. The  inventor  and  engineer  make  as  much  use  of  them, 
probably,  as  if  they  knew  their  true  nature.  The  forces  are 
employed  in  the  same  manner  that  a  carpenter  employs  his  tools. 
He  does  not  know  necessarily  how  they  were  made  or  of  what 
chemical  elements  they  consist;  but  he  makes  the  same  use,  and 
no  more  or  less  use,  of  the  tools  because  of  this  lack  of  knowl- 
edge as  to  their  inherent  nature.  So,  also,  the  nature  of  the 
power  which  prompted  Coster  to  combine  the  two  facts  is  not 
known;  but  experience  and  examples  indicate  that  this  power 
exists  and  acts  whenever  a  person  becomes  acquainted  with  such 
elementary  facts.  The  duty  of  the  future  inventor  is  to  be  awake 
to  problems  needing  solution  and  to  push  forward  to  the  attain- 
ment of  all  the  knowledge  he  can  reach;  and  he  may  continually 
feel  that  the  power  to  combine  exists  and  that  it  will  operate  as 
soon  as  those  particular  facts  are  clearly  comprehended,  which  are 
such  as  to  form,  when  combined,  an  idea. 

One  or  all  of  the  facts  may  come  by  accident,  or  by  effort, 
or  by  a  combination  of  circumstances.  In  the  particular  case 
under  consideration  the  fact  of  the  imprints  by  pressure  came 
accidentally.  The  fact  came  by  experimenting  in  the  case  of 
Humphrey  Davy's  conception  of  the  safety  lamp,  by  which  he 
became  titled  *  Sir,"  and  received  in  the  first  few  months  of  its 


133 

use  $12,000  collected  for  him  by  the  miners  of  the  country, 
who  thus  expressed  their  gratefulness.  As  in  the  case  of  Coster, 
Davy  longed  to  make  an  invention  whereby  the  fearful  and  re- 
peated losS  of  life  by  mine  explosions  would  be  prevented.  He 
was  especially  spurred  on  by  a  particular  explosion  in  which  one 
hundred  men  were  killed  in  a  single  mine  within  one  minute. 
This  made  him  the  more  eager  to  solve  the  problem.  In 
accordance  with  the  principle  already  pretty  well  established 
by  other  successful  inventors,  he  becomes  thoroughly  acquainted 
with  the  problem.  He  studies  the  causes  of  the  explosion.  He 
looks  into  the  exact  chemical  and  physical  actions  which  take 
place.  This  knowledge,  to  be  sure,  was  free  to  all;  but  he  be- 
comes acquainted  with  it,  not  simply  from  curiosity  or  for  the 
mere  sake  of  being  well  read  or  highly  educated.  He  sets  be- 
fore himself  the  knowledge  in  an  analytical  and  in  a  systematic 
manner.  He  at  last  arrives  at  the  sum  and  substance  of  the 
whole  matter  by  formulating  his  knowledge  as  a  fact.  The  "  fire- 
damp," /.  e.,  combustible  gas  escaping  within  the  mine,  mixes 
with  the  air  entering  the  mine.  When  the  proportion  of  fire- 
damp and  air  arrives  at  a  certain  relation  the  same  becomes 
ignited  by  the  miner's  lamp  and  explodes  with  great  power, 
burning  men,  clothes,  mules  and  all  else  combustible.  This  was 
one  fact  which,  coupled  with  another,  should,  according  to  the 
lessons  learned  from  Coster,  produced  the  "  idea  "  whereby  the 
mine  could  be  lighted  without  danger  of  igniting  the  mixture. 
Having  exhausted  all  book  knowledge,  he  being  a  great  student, 
he  experimented  with  the  flame  of  a  miner's  lamp  and  with  ex- 
plosive mixtures.  Systematic  and  logical  experimenting  based 
upon  previous  knowledge  of  chemical  and  physical  principles 
developed,  among  others,  two  facts,  namely:  (a)  When  two  com- 
partments are  connected  by  an  open  metal  tube,  and  filled  with 
explosive  mixtures,  the  one  may  be  lighted  and  exploded;  but 
the  flame  will  not  pass  through  the  tube  and  set  fire  to  the  mix- 
ture in  the  other  compartment,  (b)  The  flame  of  an  oil  lamp 
will  not  pass  through  a  fine  wire  gauze. 

To  know  these  facts,  and  to  know  the  fact  underlying  the 
cause  of  the  explosion  in  mines,  did  not  constitute  invention  as 
long  as  no  power  of  the  mind  acted  to  combine  them.  As  we 
may  expect,  the  power  did  act,  he  got  the  idea,  and  immediately 
planned  a  lamp  which  was  a  device  for  carrying  out  the  idea. 
The  device  has  been  modified  in  different  ways,  but  the  idea 
still  remains  the  same.  The  mind  combined  them  as  soon  as 
the  right  constitutent  facts  were  presented.  With  Coster  the 
final  wanting  fact  came  by  accident.  With  Davy  the 
final  wanting  facts  came  by  systematic  and  logical  experiment. 


134 

In  the  following  illustrations  the  wanting  fact  was  obtained  by 
a  search  of  the  old  scientific  principles  and  facts.  Most  modern 
scientific  inventions  have  been  thus  made,  as,  for  instance,  the 
telephone,  kinetograph,  incandescent  electric  lamp,  air-brake? 
telegraph,  mechanical  telephone,  steam,  air  and  gas-engines, 
artificial  ice  machine,  bleaching,  dyeing,  thermostat,  electric 
meter,  telescope,  microscope,  photography,  &c. 

Many  ideas  forming  the  foundation  of  purely  kinetic  mechan- 
ical inventions  are  compounded  in  a  similar  sense.  Lee  was  a 
fellow  or  professor  at  a  college.  He  loved  study  more  than  any- 
thing else.  As  time  passed,  he  soon  loved  a  maiden  more  than 
his  studies;  but  upon  being  married,  which  was  against  the 
rules  of  the  college,  he  was  left  without  employment,  so  that  his 
wife  was  obliged  to  take  up  her  former  employment  of  knitting 
stockings.  After  vain  attempts  in  getting  employment,  and  after 
often  watching  the  process  of  knitting,  he  recognized  how  slowly 
the  knitting  was  performed,  and  wondered  if  it  might  be  possible 
to  make  a  machine  to  do  the  work.  One  fact  he  had  to  start 
with  was  the  movement  of  the  fingers.  He  studied  the  exact 
motions  given  to  the  yarn.  He  became  perfectly  familiar  with  the 
stitches,  so  that  he  soon  knew  how  to  knit  by  hand.  This 
knowledge  constituted  one  fact;  but  he  felt  his  lack  of  the 
knowledge  of  the  remaining  fact  necessary  to  give  him  the  com- 
plete idea.  He  did  not  know  anything  about  machinery,  although 
he  felt  the  importance  of  such  knowledge  as  indicated  by  his 
looking  up  books  on  the  subject,  and  especially  by  his  visiting 
machine-shops  and  factories  and  conversing  with  mechanics. 
At  last  the  power  of  combing  facts  acted,  because  he  had  the 
two  which  were  necessary.  Learning  that  by  means  of  machinery 
any  and  all  motions  could  be  produced,  he  conceived  the  idea 
of  building  a  stocking  frame  in  which  the  motion  of  his  fingers 
would  be  performed  by  a  mechanical  device.  As  soon  as  this 
idea  occurred  to  him  the  embryo  of  the  knitting  machine  was 
created.  To  know  how  knitting  was  done  by  hand  did  not  exer- 
cise the  power  of  inventing.  To  know  that  by  mechanics  any 
combination  of  motions  could  be  produced  did  not  exercise  the 
power,  but  as  soon  as  he  knew  both  the  power  acted  apparently 
as  promptly  and  surely  as  that  of  magnetism  when  a  piece  of 
iron  is  held  near  a  magnet.  The  first  machine  was  very  crude; 
but  its  faulty  operation  indicated  where  improvements  were 
needed.  Soon  Lee  was  making  a  large  income,  and  would 
undoubtedly  have  continued  to  increase  it  except  for  com- 
petitors, there  being  no  patent  law  at  that  time.  He  next  set  up 
his  machinery  in  France,  where  he  received  a  warm  welcome 
from  Henry  the  Fourth,  during  whose  reign  Lee  and  his  family 


135 


lived  in  luxury  from  the  profits  of  this  business  in  manufacturing 
his  stocking  frame. 


CHAPTER  XV. 
FAILURE  AND  SUCCESS. 


IF  you  invent  that  which  proves  to  have  been  invented  be- 
fore, do  not  lose  courage;  but  rather  let  it  be  the  means  of 
showing  you  that  you  are  an  inventor,  and  that  the  more  inven- 
tions you  make,  the  more  likely  you  will  be  to  obtain  novelty, 
as  well  as  usefulness.  This  principle  is  substantiated  by  the 
case  of  Galling,  the  inventor  of  the  improved  gun.  He  first  in- 
vented the  propeller  wheel,  in  the  form  in  which  it  is  now  used, 
but  in  applying  for  a  patent  found  that  Ericcson  had  forestalled 
him.  The  disappointment  and  mortification  of  this  failure  were 
severe,  because  he  foresaw  the  importance  of  the  new  method 
of  propulsion;  but  with  youth  and  energy  he  overcame  its  de- 
pressing effect.  During  the  next  few  years  he  made  inventions, 
which  became  introduced  into  practice,  and  finally,  invented 
and  patented  the  gun,  which  now  bears  his  name. 

This  is  a  good  principle  upon  which  to  act.  If  anticipated, 
give  in,  and  concede  priority,  as  you  have  nothing  else  you  can 
do,  unless  you  can  prove  priority  by  proper  evidence.  Again, 
do  not  spend  years  upon  one  subject,  exclusively  of  others. 
Perhaps  your  problem  belongs  to  the  same  class,  practically,  as 
those  of  the  Philosopher's  Stone;  Quadrature  of  the  Circle;  The 
Fourth  Dimension;  The  Precise  Solution  of  Equations  of  the 
Fifth  Degree;  or  Perpetual  Motion. 

Over  a  century  ago,  Hartman  became  so  discouraged,  because 
he  could  not  solve  the  problem  of  Perpetual  Motion,  that  he 
went  and  hanged  himself,  and  only  lately  a  believer  in 
the  same  problem  committed  suicide  in  the  city  of  my 
residence,  leaving  evidence,  that  his  reason  for  so  doing,  was  his 
disappointment  in  life,  because  he  could  not  produce  perpetual 
motion.  I  do  not  intimate  that  any  one  of  my  readers  is  under- 
taking impossibilities ;  but  they  may  be  wasting  time  in  a  path 
in  which  others,  for  scores  of  years,  have  failed.  I  mention,  as 
an  example,  thermo-electricity,  by  contact  of  different  metals. 
Give  it  up  !  but  if  you  wish  to  work  on  this  subject,  in  general, 
try  the  solution  of  conversion  of  heat  into  electricity,  in  some 
other  line  than  by  the  contact  of  different  metals.  Clamond 


136 

spent  thirty-five  years  on  thermo-electricity  with  scarcely  any 
improvement  over  his  predecessors. 


CHAPTER  XVI. 
SIMULTANEOUS  INVENTIONS. 


THE  preceding  chapter  illustrates  that  Gatling  would  have 
been  credited,  both  by  honor  and  money,  through  his  method  of 
boat  propulsion,  if  Ericcson  had  never  been  born.  The  element 
of  time,  alone,  lost  him  his  right  to  a  patent.  The  system  of 
duplex,  and  multiplex  telegraphy  was  invented  almost  simul- 
taneously, and  independently,  by  four  individuals,  in  different 
countries.  I  know  of  a  certain  inventor  whose  six,  out  of  fifty 
applications,  have  come  into  interference  with  pending  applica- 
tions in  the  Patent  Office.  A  count  of  the  number  of  interfer- 
ence cases  in  the  U.  S.  Patent  Office,  would  amount  probably  to 
several  hundred  per  year. 

These  facts  establish  the  following  principles  : — 

Important  inventions  are  often  made  by  independent  invent- 
ors, at  approximately  the  same  time. 

I  do  not  as  a  rule  enter  into  argument  upon  the  principles  I 
state,  as  I  undertake  to  establish  them  upon  facts;  but  this  is 
such  a  curious  principle,  that  I  cannot  refrain  from  theorizing, 
slightly.  As  soon  as  a  large,  influential,  electric  company  intro- 
duces the  alternating  electric  current  into  commerce,  inventors 
naturally,  and  simultaneously,  turn  their  attention  to  electric 
converters,  alternating  current  meters,  and  motors,  and  to  vari- 
ous other  devices  peculiar  to  an  alternating  current.  When  any 
generic  invention  is  introduced,  it  is  easy  to  see  that  inventors 
undertake,  simultaneously,  to  get  a  patent  upon  the  best  specific 
way  of  carrying  out  the  generic  invention.  Such  inventions 
have  profited  enormous  fortunes. 

In  view  of  the  last  principle,  inventors  cannot  be  too  careful 
and  quick  in  having  their  inventions  properly  described  and  at- 
tested, even  if  they  do  not  apply  for  a  patent  immediately.  The 
drawings  and  description  of  the  first  mental  invention  should 
be  signed,  witnessed,  and  executed  before  a  notary  public,  if 
possible,  on  the  day  of  conception. 

A  study  of  Camille  A.  Faure's  wonderful,  but  simple,  im- 
provement upon  Plante's  electrical  storage  system  establishes  a 
valuable  principle.  The  latter  experimented  several  years  upon 


137 

the  storage  battery,  his  object  being  the  determination  of  the 
best  metals  to  be  employed  as  electrodes.  He  did  not  proceed 
as  an  inventor.  He  worked  more  as  an  investigator.  He  tried 
silver,  gold,  platinum,  and  other  metals  in  the  same  manner  that 
an  engineer  would  test  samples  of  wire,  in  order  to  pronounce 
which  is  the  best.  Plante  learned  that  lead  was  superior  to  all 
other  metals.  To  form  a  battery,  he  would  pass  a  current 
through  the  plates  immersed  in  dilute  sulphuric  acid,  continuing 
the  current  for  several  days.  Then  the  battery  would  be  dis- 
charged, by  allowing  the  current  to  escape  through  a  resistance. 
The  operation  would  be  repeated  until  a  sufficient  layer  of  active 
material  was  formed  upon  the  surface  of  the  lead  plates. 
The  manufacture  of  a  large  battery  would  occupy  about  three 
months,  and  would  consume  nearly  as  much  electrical  energy  as 
the  device  would  yield  during  its  lifetime.  These  experiments 
were  made  thirty  years  ago.  Only  comparatively  lately,  Camille 
A.  Faure,  whose  name  is  now  so  familiar,  considered,  analyti- 
cally, the  question  of  secondary  currents,  for  the  purpose  of  put- 
ting the  storage  system  on  a  commercial  basis.  He  recognized 
the  importance  of  understanding  the  exact  chemical  nature  of 
the  secondary  battery.  He  considered  carefully  just  what 
chemicals  existed,  when  charged,  and  when  discharged.  Faure 
learned  that  this  material  consisted  of  a  mixture  of  the  lower 
oxides  of  lead,  as  common  red  lead  and  litharge.  Consequently, 
when  he  found  after  discharge,  that  the  substances  were  red  lead 
and  litharge,  how  easy  it  was  for  him  to  go  to  a  paint  store  and 
get  these  materials,  and  apply  them  to  the  lead  plates  in  the 
course  of  a  few  minutes,  and  at  the  same  time  have  a  thickness 
of  active  material,  sufficient  to  store  as  much  electricity  as 
would,  by  the  Plante"  process,  occupy  perhaps  six  months.  If 
Faure  had  not  taken  the  trouble  to  find  out  the  exact  chemical 
composition  of  the  materials  existing,  at  different  stages,  in  the 
Plante  battery,  it  is  safe  to  say  that  he  would  not  have  made  the 
wonderful  improvement  he  did.  The  converse  is  also  apparently 
true.  He  made  the  invention,  principally,  because  he  took  the 
pains  and  trouble  to  find  out,  by  ordinary  means,  the  exact  com- 
position and  chemical  reactions  in  the  Plant£  battery.  .Before 
formulating  a  principle  upon  this  single  example,  let  another 
case  be  considered,  in  order  to  obtain  a  second  fact  for  estab- 
lishing the  principle. 

The  invention  considered  is  that  of  the  first  dynamo.  Dr. 
Pacinotti,  of  Florence,  constructed  an  electric  motor,  which 
antedated  the  dynamo.  He  studied  the  motor  from  the  stand- 
point of  an  inventor.  He  analyzed  the  electrical  changes  which 
took  place  in  the  motor,  in  view  of  improving  the  same,  and  then 


138 

constructed  a  greatly  improved  form.  To  show  how  well  he 
knew  the  scientific  principles,  he  suggested  in  a  publication,  that 
if  a  certain  minute  change  were  made  in  his  motor,  and,  instead 
of  passing  a  current  through  the  same  and  obtaining  power,  he 
believed  that  he  could  apply  power,  and  obtain  an  electric  cur- 
rent. Gramme  acted  upon  this  suggestion  and  thus  was  born 
the  first  dynamo. 

Do  not  trust  to  accident,  nor  to  inspiration,  nor  to  any  myth- 
ical spirit  or  genius  to  make  your  invention  for  you.  Do  not 
expect  the  invention  to  come  to  you,  without  any  exertion  on 
your  part.  For  thirty  years  the  electric  motor  was  known,  but 
was  not  operated  by  power  to  obtain  a  current.  For  thirty  years 
the  red  lead  and  litharge  occurred  on  the  lead  plates,  after  dis- 
charge. Obtaining,  with  a  view  to  invention,  an  accurate  knowl- 
edge of  the  scientific  nature  of  the  electric  motor,  and  of  the 
early  secondary  battery,  was  the  factor  which  suggested  the  re- 
spective inventions. 

The  rules  based  upon  the  above  principle  maybe  formulated 
thus  :— 

As  soon  as  any  one,  either  by  investigation,  alone,  or  with 
the  assistance  of  a  chemist  or  physicist;  or  as  soon  as  a  scientist, 
or  any  individual,  announces  a  scientific  fact,  or  principle  not 
known  before;  embrace  the  opportunity  of  being  the  first  to 
apply  the  fact,  or  principle,  to  a  useful  purpose.  In  reading 
periodicals,  or  scientific  papers,  have  this  rule  of  invention  in 
view.  Look  out  for  the  results  of  scientific  investigation,  not  as 
a  student,  who  simply  reads  as  a  matter  of  obtaining  knowledge; 
nor  as  a  critic;  nor  as  a  pastime;  but  for  the  single,  and  concen- 
trated purpose  of  being  the  pioneer  in  the  application.  As  soon 
as  Faure  made  his  invention,  there  were  scores  of  immediate, 
and  independent,  inventors,  who  conceived  the  improvement  of 
compressing  the  active  material  into  small  cells,  or  perforations, 
in  the  lead  plate,  for  the  two-fold  advantage  of  obtaining  more 
metallic  surface,  and  of  retaining  the  active  material  in  its  pro- 
per place;  since,  if  applied  to  a  flat  lead  surface,  it  is  apt  to  fall 
off  gradually  but  surely. 

The  question  is  sometimes  asked  by  the  thoughtless,  of  what 
use  is  it  to  spend  a  fee  to  belong  to  an  electrical  society;  or  to 
be  a  subscriber  to  a  scientific  paper  ?  The  man  who  wishes  to 
be  a  successful  inventor  cannot  afford  to  despise  such  things. 

The  history  of1  the  invention  of  the  carbon  transmitter 
strengthens  the  above  rule  of  invention.  In  1873  Edison  dis- 
covered the  scientific  principle  that  all  semi-conductors  have  the 
property  of  varying  the  current,  according  to  the  pressure  upon 
two  pieces  in  loose  contact  and  in  an  electric  circuit.  Four 


139 


years  later,  when  inventing  in  the  subjects  of  telephones,  he  re- 
called the  new  knowledge,  and  by  introducing  semi-conductors 
into  a  circuit,  and  talking  against  them,  he  thereby  applied  the 
new  knowledge  to  a  useful  purpose. 


CHAPTER  XVII. 
SIMPLICITY  THE  RESULT  OF  SPECIFIC  INVENTION. 


IT  is  a  principle  that  the  final  type  is  simpler  in  construction 
than  the  generic  invention. 

The  first  telephone  transmitter  was  more  cumbersome  and 
costly  than  the  present;  while  the  first  envelope-machine  was  as 
confusing  in  appearance  as  the  wisps  of  hay  in  a  haystack. 
Many  men  wonder  why  they  could  not  have  invented  the  tele- 
phone. They  should  be  reminded  of  two  things:  they  either  did 
not  try,  or  else  they  think  that  the  first  unsuccessful  telephones 
were  as  simple  as  the  present  one. 

Nearly  every  physical  invention  is  at  first  of  low  efficiency, 
complex  and  intricate  in  construction,  and  tending  very  much 
to  drive  the  inventor  into  despair.  If  he  has  evidence  that  he  is 
on  the  right  track,  he  should  not  stop  for  such  difficulties,  by 
abandoning  the  invention  and  finding  afterwards  that  others 
commenced  where  he  left  off  and  succeeded.  It  is  far  better,  as 
a  last  resort,  to  get  the  assistance  of  another  inventor  at  the  ex- 
pense of  a  portion  of  the  interest  in  the  patent,  and  act  thereby 
in  accordance  with  the  old  proverb  that  "  two  heads  are  better 
than  one." 


CHAPTER  XVIII. 
THE  AGE  OF  INVENTION. — A  CAUSE  OF  INVENTION. 


THE  world  has  had  its  age  of  national  wars;  its  age  of  geo- 
graphical discovery,  as  at  the  time  of  Columbus  when  the  whole 
of  the  Eastern  Continent  seemed  to  give  up  everything  and  try 
to  claim  America;  its  age  of  scientific  discovery,  right  after  the 
time  of  Bacon,  when  physical  and  chemical  sciences  grew  faster 
than  ever  before;  its  age  of  religious  war  which  seems  now  to  be 


140 

passing  away,  and  being  replaced  by  a  tone  of  greater  toleration; 
its  age  of  the  gold-mining  panic;  and  now  its  age  of  invention. 
Each  invention  is  the  embryo  of  another  invention.  Electric 
lighting  begets  hundreds  of  detail  inventions  and  improvements, 
and  so  with  other  new  arts  and  industries. 

Sometimes,  and  especially  in  the  early  days  of  the  age  of  in- 
vention, several  generations  were  occupied  in  the  perfection  of 
an  invention.  In  one  generation  the  mental  invention  is  made. 
In  the  second,  the  crude  generic  invention;  and  in  the  third, 
the  perfected,  specific  form.  Thus  it  was  with  the  screw  pro- 
peller. The  steam  engine  inventor,  Watt,  wrote  to  Dr.  Small  in 
1770,  "  Have  you  ever  considered  a  spiral  oar  for  that  purpose  ? " 
(of  propelling  boats).  In  1834,  Francis  Pettit  Smith  constructed 
a  boat  propelled  by  a  wooden  screw,  driven  by  a  wound-up 
spring.  Later  he  built  a  large  boat  and  exhibited  it  on  a  canal, 
using  steam  power.  A  few  years  later  Ericcson  constructed,  and 
patented,  and  introduced  the  specific  form  in  use  at  present. 

From  the  time  that  Harrison  began  to  invent  and  perfect 
the  chronometer,  for  use  at  sea,  and  obtained  his  reward  of  $50- 
ooo  from  the  English  Government,  forty-five  years  elapsed. 
He  should  have  received  $100,000,  as  that  was  the  reward 
offered.  The  good  King  of  Sardinia,  however,  bought  four  of  his 
chronometers,  paying  voluntarily  $20,000  for  them,  stating  that 
it  was  a  small  recompense  for  the  time  spent  by  him  for  the 
general  good  of  mankind.  As  contrasted  with  the  above  almost 
ancient  inventions,  it  is  very  striking  to  note  the  rapidity  with 
which  our  present  inventors  complete  the  commercial  specific 
invention  and  reap  the  fruits  of  their  labors. 


CHAPTER  XIX. 
THE  GOVERNMENT  FAVORABLE  TO  INVENTORS. 


THE  Government  not  only  protects  an  invention  by  a  patent, 
but  also  by  requiring  duty  paid  upon  certain  articles  manufac- 
tured in  a  foreign  country.  Six  years  ago  I  ordered  an  Ayrton 
and  Perry  voltmeter  from  England  and  paid  $20  duty,  which 
now  goes  as  profit  to  the  American  inventor,  since  the  American 
style  has  become  so  popular;  consequently  the  inventor  is  bene- 
fited very  directly.  The  new  duty  on  tin  is  so  high  that  capital- 
ists have  incorporated  companies  for  mining  tin  in  the  United 
States,  where  its  ore  occurs  abundantly.  This  opens  a  new  field 


141 

for  the  inventor  to  experiment  and  produce  the  best  process  for 
the  particular  kind  of  ore  found  in  this  country.  No  wonder 
the  people,  through  the  Government,  favor  the  inventor.  Two- 
thirds  of  the  wealth  of  this  country  are  due  to  invention.  The 
wonderful  invention  of  the  telephone  is  a  self-evident  proof  of 
the  value  of  Government  protection  and  encouragement  to  in- 
ventors. Howe  made  one  million  dollars  from  his  invention 
relating  to  sewing  machines.  Many  of  my  acquaintances  have 
made  fortunes  from  patented  inventions.  Smaller  inventions 
also  have  a  remarkable  record.  The  rubber  mat,  with  projec- 
tions for  receiving  coins,  netted  a  handsome  income  to  the  in- 
ventor and  large  profits  to  those  who  promoted  its  interest; 
while  its  convenience  to  storekeepers  was  a  great  benefit  to  the 
public. 

Certain  detail  improvements  in  primary  batteries,  electric 
switches,  telegraph  relays,  telephonic  apparatus,  electric  door 
openers,  insulators,  dynamos,  motors,  electric  lamps,  &c.,  have 
handsomely  rewarded  the  inventor  through  royalties,  stock,  or 
cash.  Even  such  small  inventions  as  toys  are  of  much  benefit 
to  children,  not  only  in  amusing  them  but  in  the  relief  they 
bring  to  mothers  and  guardians;  also  in  the  instruction  they 
quietly  but  forcibly  bestow  upon  children.  The  ball  and  elastic, 
which  cost  but  one-quarter  of  a  cent  to  manufacture,  netted  a 
fortune  to  the  patentee  and  manufacturer.  The  lead  pencil, 
with  rubber  tip,  brought  $100,000  to  the  inventor.  Copper  tips 
for  shoes  netted  millions,  and  such  an  apparently  valueless 
device  as  the  dancing  jim-crow  paid  yearly  $75,000.  Large 
fortunes  were  also  made  from  Pharaoh's  serpents;  the  Wheel 
of  Life;  the  pencil  sharpener;  the  gimlet  screw;  powdered 
emery  on  cloth;  and  the  rivet  and  eyelet  for  clothing. 

At  the  end  of  the  next  seventeen  years,  especially  in  the 
electrical  industry,  larger  profits  than  ever  can  probably  be 
named  as  coming  to  inventors  from  their  inventions,  judging 
from  the  speed  with  which  so  many  are  even  now  reaping  the 
benefits  of  their  brain.  In  view  of  the  vast  benefits  directly  to 
inventors  and  also  to  the  people,  I  advise  favoring  all  bills  and 
laws  for  the  protection  of  inventions  and  industries.  To  be  sure 
the  people  are  taxed.  A  person  pays  more,  on  the  average,  for  a 
patented  article  than  after  the  patent  expires;  but  they  can 
afford  it  on  account  of  the  superiority  of  the  patented  device; 
and  they  should  pay  extra  for  the  sake  of  encouragement  to 
inventors.  It  is  argued  that  inventors  invent  for  the  love  of  in- 
venting; but  why  do  they  have  the  love.  Many  love  their  busi- 
ness; but  why  ?  Many  love  to  be  engaged  in  writing  novels  or 
other  books.  Many  love  to  be  Senators  and  Presidents.  Their 


142 

love  depends  upon  several  elements,  but  an  important  one,  when 
honestly  stated,  is  a  substantial  reward.  Acting  on  this  prin- 
ciple, foreign  countries  and  societies  have  offered  rewards  to  the 
inventor  first  solving  successfully  a  given  problem.  Dr.  Vander 
Weyde  has  stated,  in  a  conversation  on  this  subject,  that  France 
offered  $100,000  to  him  who  would  make  a  commercially  suc- 
cessful motor.  That  was  at  the  time  when  the  electric  motor 
was  in  its  infancy.  Societies  and  corporations  have  made  simi- 
lar offers  at  various  times  and  in  various  countries;  it  is  an 
admirable  plan,  but  the  inventor  should  consider  himself  fortu- 
nate that  he  is  not  dependent  upon  that  kind  of  reward.  The 
experience  of  all  countries  has  shown  that  the  inventor  is  most 
effectually  encouraged  by  rewarding  him  a  patent  which  he  can 
negotiate  as  a  piece  of  personal  property,  at  his  own  terms,  in 
his  own  name,  and  at  such  a  time  best  suited  to  his  interests,  all 
according  to  the  value  of  the  invention  which  is  covered  by  the 
patent. 


CHAPTER    XX. 

INVENTION  AND  CAPITAL. 


INVENTORS  continue  to  invent!  Capitalists  continue  to  invest! 
I  am  personally,  acquainted  with  an  individual  who,  in  the  early 
days  of  the  telephone,  was  offered  one-quarter  interest  in  the 
patent  for  $1,500.  To  another  party,  it  is  reported,  the  rights 
for  the  whole  of  New  Jersey  were  offered  for  a  mere  nominal 
sum. 

Inventors  and  capitalists  should  be  more  willing  to  co- 
operate. It  is  too  often  the  case  that  the  former  must  pay  for 
his  own  experiments  and  patent  costs  before  a  capitalist  will 
even  take  the  trouble  to  look  into  the  merits  of  the  alleged 
invention.  On  the  other  hand,  it  is  too  often  true  that  the 
capitalist  seeks  to  join  with  the  inventor,  but  the  latter  wants 
too  high  a  price  at  the  beginning. 

Referring  to  the  beginning  of  'this  paper,  you  remember  I 
stated  the  necessity  of  "confidence  in  success."  This  principle 
applies  equally  well  to  capitalists.  Let  them  join  with  and 
encourage  the  inventor.  Let  them  take  an  interest,  by  assign- 
ment, and  pay  for  expenses  in  the  premises.  Brains  and 
knowledge  are  valuable  and  necessary  and  are  the  primary 
cause  of  invention,  but  the  inventor  cannot  obtain  protection 


143 


and  try  his  invention  practically  without  money.  I  say  to  in- 
ventors and  capitalists  join  hands,  not  merely  as  a  trial,  but 
with  a  determination  to  succeed.  Put  up  a  few  hundred  dollars 
on  scientific  books  and  electrical,  chemical  and  physical  appar- 
atus for  some  promising  inventor.  If  you  wait  until  he  shows 
the  value  of  his  invention,  you  will  find  the  price  for  an  interest 
is  more  than  you  care  to  pay.  Successful  inventors  have  almost 
universally  had  the  assistance  of  capitalists;  not  after  grant  of 
patent  and  proof  of  success;  not  after  the  inventor  acquired 
fame,  but  at  the  time  of  the  embryo  of  the  invention. 

Men  of  capital  have  more  confidence  at  present  in  proposed 
inventions  than  in  the  time  of  Murdock,  the  inventor  of  artificial 
lighting  by  gas.  Sir  Humphrey  Davy  asked  Murdock  if  he  ex- 
pected to  use  the  dome  of  St.  Paul  for  the  gas  holder.  Sir 
Walter  Scott  made  many  clever  jokes  about  it.  Wollaston 
declared  that  they  might  as  well  try  to  light  London  by  a  slice 
from  the  moon  as  to  send  the  light  through  the  streets  in  pipes. 
John  Wilkenson  prophesied  of  the  proposed  ship  of  iron,  "  It 
will  be  only  a  nine  days'  wonder,  and  afterwards  a  Columbus's 


CHAPTER    XXI. 
ACCIDENTAL  INVENTING  EXCEPTIONAL. 


EVERY  invention,  before  the  introduction  into  practical  use, 
passes  through  two  stages,  namely,  mental  and  physical. 

An  invention  is  mental  when  it  exists  as  an  imagination  or 
conception  in  the  mind  of  the  inventor. 

An  invention  is  physical  when  the  mental  invention  is  put 
into  bodily  form  by  hand,  or  by  hand  with  the  assistance  of  a 
convenient  tool. 

A  mental  invention  sometimes  does  not  become  a  physical 
invention.  The  laws  of  nature  may  not  permit  its  operative, 
physical  construction.  An  example  is  that  of  perpetual  motion. 
In  the  U.  S.  Patent  Office  are  hundreds  of  applications  for 
devices  claimed  to  produce  motion  and  force  forever  when  once 
started.  The  simplest  form  of  such  an  invention  is  a  wheel 
mounted  upon  a  shaft  or  axle.  The  same  would  rotate  forever, 
when  once  started,  if  it  were  not  for  the  retarding  forces  of  fric- 
tion, resistance  of  the  air,  and  imperfections  more  or  less  due  to 
mechanical  construction.  I  know  of  a  case  where  a  certain 


144 

business  man,  who  had  sufficient  brains  and  education  to  obtain 
his  wealth,  was  induced  by  one  possessed  of  a  mental  perpetual 
motion  invention  to  expend  two  thousand  dollars  in  the  con- 
struction of  the  physical  invention.  The  wheel,  upon  which 
balls  and  chains  and  mercury  were  to  operate,  was  so  large  that 
in  one  turn  it  would  travel  fifty  feet.  It  was  proposed  to  em- 
ploy this  device  principally  to  propel  railway  trains. 

A  Canadian  noticed  that  by  means  of  a  tackle  a  man,  weigh- 
ing one  hundred  and  fifty  pounds,  raised  a  weight  of  six  hundred 
pounds,  and  after  he  had  induced  some  men  to  construct  an 
alleged  automatic  force-creating  machine  at  great  expense, 
they  came  to  the  sorrowful  conclusion  that  perpetual  motion 
machines  were  not  practical,  however  inviting  the  mental 
invention. 

A  mental  invention  sometimes  does  not  become  a  physical 
invention  because  the  inventor  lacks  money,  technical  knowl- 
edge, or  diligence.  Such  a  mental  invention  often  becomes  a 
physical  invention  by  the  assistance  of  a  capitalist,  an  educated 
person,  or  a  diligent  companion. 

A  mental  invention  fails  often  to  become  a  physical  inven- 
tion because  it  falls  short  of  completeness.  It  is  then  more 
properly  called  an  idea.  It  lacks  some  one  or  two  elements  to 
be  supplied,  perhaps,  many  years  later  either  by  the  same  in- 
ventor or  by  another. 

The  telephone,  as  a  physical  invention,  was  a  conveyer  of 
musical  and  vowel  sounds  before  it  could  transmit  articulate 
speech,  and  yet  the  mental  invention  included  both,  and  par- 
ticularly the  latter. 

A  mental  invention  of  one  person  often  fails  to  become  a 
physical  invention  because  of  anticipation  by  a  prior  inventor. 
The  later  inventor  either  abandons  the  case  or  proceeds  to 
undertake  to  prove  priority  of  invention. 

Having  shown  that  an  invention  may  be  either  a  mental  in- 
vention or  a  physical  invention,  and  that  it  must  first  be  mental 
before  it  can  be  physical,  it  becomes  necessary  to  state  the  ex- 
ception to  this  principle.  The  exception,  however,  very  seldom 
occurs.  It  is  sometimes  remarked  that  the  inventor  stumbled 
upon  the  invention  while  experimenting  upon  some  independent 
invention;  or,  that  he  made  it  purely  by  accident — without 
thinking.  Certain  chemical  compounds  have  been  made  with- 
out any  prior  idea  on  the  part  of  the  inventor  as  to  the  result 
of  mixing  the  elements  to  produce  the  compound,  and  also  with- 
out any  idea  as  to  its  usefulness  and  novelty.  In  this  manner 
Bunsen  discovered  that  freshly  precipitated  oxyhydrate  of  iron 
is  an  excellent  antidote  for  arsenic  poison.  This  accidental  or 


145 


stumbling  method  of  inventing  is  very  exceptional,  especially  in 
modern  inventing. 

&  Professor  Brackett  of  Princeton  College  recognizes  this  truth 
as  based  upon  the  experience  of  former  inventors.  He  says  in 
regard  to  Volta's  invention,  "It  was  not  the  mere  outcome  of 
happy  accident,  but  the  result  of  severely  logical  reasoning  upon 
the  facts  which  he  had  observed  while  he  was  investigating  the 
so-called  animal  electricity'  of  Galvani." 


CHAPTER  XXII. 

WOMEN  INVENTORS. 


THE  United  States  Official  Gazette  puplished  the  following: 

"  The  Patent  Office  has  published,  and  has  for  sale,  a  vol- 
ume containing  a  list  of  women  inventors  to  whom  patents  have 
been  granted,  from  1790  to  July  i,  1888." 

Investigation  shows  the  approximate  number  of  women 
patentees  in  the  United  States  to  the  present  date,  to  be  2,400, 
and  that  the  prevailing  departments  of  art,  in  which  they  work, 
are  kitchen  utensils  ;  articles  of  dress  ;  fabrics  ;  toys  ;  hospi- 
tal appliances  ;  and  educational  devices,  especially  ;  but,  scat- 
tered here  and  there  we  find  nearly  every  department  repre- 
sented. By  far  the  larger  portion  is  domestic.  The  total  num- 
ber of  men  patentees  in  the  United  States  in  the  rough  is  greater 
than  the  population  of  New  York  City. 

The  woman  inventor  of  the  fluting  iron  made  a  handsome 
fortune,  while  those  interested  with  her  were  equally  profited. 
This  is  only  one  case  out  of  many  similar  successes  of  women 
inventors. 

Some  women,  of  course,  are  overworked,  and  some  so  busy 
with  various  matters  that  little  time  and  strength  are  left  for  the 
task  of  inventing  ;  but  there  are  thousands  of  intelligent,  edu- 
cated, and  especially  wealthy  women,  who  have  more  time  to 
spare  than  men  of  the  same  standing,  and  these  women  wishing 
often  for  some  employment,  either  for  the  sake  of  occupation  or 
profit,  waste  their  time  waiting  for  something  to  turn  up.  The 
chance,  in  other  directions,  for  women  to  gain  fame  or  wealth 
is  very  limited  in  comparison  to  the  opportunities  for  men.  The 
former  are  confined  mostly  to  literature,  painting  and  music.  In 
conversation  with  women  on  this  subject  they  almost  universally 
excuse  themselves,  or  mourn  their  incapacity,  on  the  ground 


146 

that  they  have  no  genius  or  gift  for  inventing.  They  might  as 
well  wait  for  a  piano  to  teach  them  to  play,  without  practice,  as 
to  wait  for  an  invention  to  come  to  them  without  action.  They 
should  have  a  certain  amount  of  conceit,  and  try  in  every  way,- 
and  especially  by  practice,  and  systematic  thought,  to  invent 
something  which  will  overcome  an  existing  difficulty.  Not  only 
is  there  a  prospect  of  reward,  but  the  very  act  of  developing  a 
conception  begets  probably  the  highest  type  of  earthly 
happiness. 

One  reason,  as  exhibited  from  the  study  of  inventions,  why 
women  are  not  more  prominent  among  inventors,  is  that  upon 
finding  a  difficulty  to  be  overcome,  and  abandoning  conceiving 
the  possibility  of  success,  she  immediately  explains  it  to  her  hus- 
band, or  son,  who  dwells  upon  the  subject  until  developed  into 
a  complete  invention,  showing  again  the  want  of  confidence  in 
herself.  Do  not  be  surprised  if  the  invention  is  not  developed 
and  perfected  in  a  day.  It  is  said  that  inventor  Bell's  father 
tried  to  transmit  speech,  and  that  the  son  followed  in  his  foot- 
steps many  years  before  success.  It  needs  confidence  and  per- 
severance, more  than  luck  or  the  indefinite  quantity  called 
genius.  All  women  have  the  gift ;  but  they  will  never  realize 
it,  until  they  have  confidence,  and  practice  with  great 
perseverance. 

I  think  it  will  be  admitted  that  some  of  the  greatest  difficul- 
ties with  the  natural  laws,  are  met  with  in  the  kitchen.  The 
domestics  are  probably  not  more  to  blame,  than  those  who 
ought  to  invent  devices,  which  would  relieve  some  of  the  heavy 
responsibilities  placed  upon  the  employed,  who  usually  lack  in- 
telligence, education,  memory,  &c.,  more  than  they  do  the  moral 
virtues,  such  as  obedience,  &c.  Servants  formerly  burned  milk. 
Now  they  have  the  device  where  the  milk  is  heated  by  boiling 
water,  so  that  burning  becomes  impossible  ;  because  it  is  a  scien- 
tific fact  that  milk  cannot  be  heated  to  212°  Fahrenheit  in 
a  vessel  standing  in  water,  and  not  hermetically  sealed.  The 
milk  heater  is  therefore  a  great  invention  since  it  does  not  allow 
a  servant  to  burn  milk.  The  improved  coffee  pot,  whereby  the 
disagreeable  and  unwholesome  elements  of  the  coffee  are  re- 
moved, is  likewise  a  remarkable  invention.  Some  servants  can 
make  good  bread,  and  others,  equally  competent  in  other  things, 
cannot.  This  is  a  difficulty  which  I  believe  is  not  an  impossi- 
bility to  overcome.  Some  apparatus  should  be  invented,  so  that 
any  person,  by  obeying  certain  simple  rules,  can  operate  it, 
and  produce  bread  of  the  best  quality.  While  staying  at  a  board- 
ing house  during  college  life,  the  bad  bread  was  successively 
due,  according  to  the  landlady,  "  to  anew  barrel  of  flour,"  "new 


147 


girl,"  "  the  dough  stood  too  long,  or  too  short  a  time,"  "pota- 
toes were  inadvertently  omitted,"  "trying  a  new  yeast  cake," 
"  the  oven  wasn't  hot  enough,"  etc. 


CHAPTER  XXIII. 

PROBLEMS  IN  INVENTION. 


IF  inventors,  and  those  who  have  a  love  for  inventing,  were 
more  generally  acquainted  with  the  problems  known  only  by  a 
comparatively  few,  progress  in  inventing  would  be  much  more 
rapid  and  superior.  One  man  may  not  be  able  to  solve  a  prob- 
lem, although  he  has  worked  at  it  for  weeks;  whereas  another, 
having  special  experience  in  another  department  of  industry,  may 
start  in  a  radically  new  direction  and  solve  the  problem  success- 
fully. The  mere  mention  of  a  difficulty  is  such  an  assistance 
that  the  one  who  names  the  problem  is  often  (but  not  rightfully) 
accredited  as  the  inventor.  An  attempt  was  made  at  the  Patent 
Centennial  at  Washington,  in  1891,  to  prove  that  the  widow  of 
General  Greene  was  the  inventor  of  the  cotton  gin.  She  was 
merely  the  one  who  pointed  out  how  important  a  machine  would 
be  which  would  clean  cotton  from  its  seed.  The  story  of  Whit- 
ney's invention  illustrates  how  necessary  it  is  that  the  multi- 
tude should  be  acquainted  with  existing  problems.  Mrs.  Greene, 
herself,  although  recognizing  the  difficulty,  was  void  of  the 
knowledge  of  mechanics,  and  therefore  did  not  possess  the  quali- 
fication for  designing  any  machine  whatever.  The  story  is  told 
thus  by  the  son  : 

"  Eli  Whitney,  the  sole  inventor  of  the  cotton  gin,  was  spend- 
the  winter  of  1793  in  the  family  of  Mrs.  Greene,  on  her  planta- 
tion, '  Mulberry  Grove,'  eleven  miles  from  Savanah,  Ga.  On  one 
occasion  she  had  a  number  of  officers  who  had  served  in  the 
army  under  General  Greene  meet  at  her  house  to  dine.  They 
were  Southern  planters,  and  in  the  course  of  conversation  at  the 
table  were  lamenting  the  destitution  of  the  South,  saying  that 
corn  and  indigo  were  the  only  crops— that  the  negroes  ate  up 
the  corn,  and  that  the  price  of  indigo  was  so  low  that  its  culture 
did  not  pay,  but  if  some  machine  could  be  devised  for  cleaning 
upland  cotton  from  its  seed,  they  could  all  improve  their  condi- 
tion and  make  slave-labor  profitable.  The  hostess,  Mrs.  Greene, 
referred  them  to  her  young  friend  Whitney,  who  was  present, 


148 

saying  that  he  could  make  such  a  machine;  that  he  could  invent 
anything  in  the  mechanical  line — which  Mr.  Whitney  modestly 
disclaimed.  But  this  incident  first  called  his  attention  to  this 
great  want,  and  its  importance,  if  successful.  He  had  recently, 
graduated  at  Yale  College,  and  was  preparing  to  study  law. 
However,  he  resolved  to  devote  himself  for  a  time  to  this  inven- 
tion, and  in  consequence  went  to  Savannah,  searching  the  ware- 
houses there  to  find  some  cotton  in  the  seed,  which  he  had  never 
seen.  At  length  he  found  a  small  quantity,  and  devoted  the 
rest  of  the  winter  to  his  invention,  and  produced  the  cotton  gin, 
the  same  that  is  in  general  use  to-day,  virtually  unimproved 
upon.  He  had  invented  the  breast  of  the  machine,  with  its 
toothed  cylinder  and  hopper,  and  was  thinking  how  he  should 
dispose  of  the  cotton  when  on  the  cylinder  of  saw-teeth,  after 
it  had  been  separated  from  the  seed.  Mrs.  Greene,  who  was 
watching  the  progress  of  the  invention  with  great  interest,  play- 
fully took  up  a  hearth-brush  and  said  :  '  I  can  get  rid  of  the  cot- 
ton on  the  cylinder,'  and  began  to  brush  it  off,  probably  not 
having  the  remotest  idea  of  a  revolving  brush,  but  Whitney  con- 
ceived the  idea  of  a  revolving  brush  and  applied  it.  But  the 
brush  does  not  constitute  a  cotton  gin  nor  separate  the  cotton 
from  its  seed.  Lord  Macauley  said  :  '  What  Peter  the  Great 
had  done  for  the  advancement  of  Russia,  the  inventor  of  the  cot- 
ton gin  has  equaled,  and  more,  in  promoting  the  power  and  pro- 
gress of  the  United  States.'  " 

MISCELLANEOUS  PROBLEMS. 

W.  C.  Barney,  in  the  ELECTRICAL  ENGINEER  (New  York), 
reminds  the  public  that  even  after  the  expiration  of  Bell's  patent 
for  transmitting  speech  by  the  use  of  an  undulatory  current  in 
a  closed  circuit  the  American  Bell  Telephone  Co.  will  order 
a  patent  to  issue  upon  the  carbon  transmitter,  which  now  forms 
the  subject-matter  of  two  applications  in  interference  and  both 
owned  by  the  Bell  Co.,  which  will  then  have  protection  for 
another  seventeen  years  upon  telephony  broadly  because  the 
other  form  of  transmitter  (the  magneto  telephone)  is  not  nearly 
as  practical.  The  problem  is  to  invent  that  which  does  not  in- 
volve the  principle  of  vibrating  the  current,  by  speaking  against 
terminals,  in  loose  contact  in  an  electric  circuit.  After  March 
7,  1893,  the  use  of  an  undulatory  current  for  transmitting  speech 
becomes  public.  The  editorial  of  the  above-named  paper  and 
the  daily  press  are  calling  loudly  for  accomplishing  the  result  of 
the  carbon  transmitter,  or  microphone,  by  a  different  device. 

Under  this  head  the  inventor  should  be  reminded  of  the 
fact  that  while  the  telegraph  will  operate  between  New  York  and 


149 

Chicago,  Omaha,  Denver  and  San  Francisco,  the  telephone  is  a 
failure  for  distances  further  than  Boston,  and  very  imperfect  for 
that  distance. 

In  the  trolley  system  for  electric  railways,  the  trolleys  now  in 
use  jump  the  wire,  the  car  stops,  and  the  trolley  must  be  re- 
placed. This  objection  should  be  remedied. 

Ferry-boats  are  seldom  known  to  be  injured  in  collisions. 
Why  should  not  the  problem  be  solved  of  constructing  ocean 
steamers  or  providing  attachments  whereby  they  are  not  so  often 
sunk?  The  compartment  invention  is  a  step  in  this  direction. 

Women  are  greatly  annoyed  by  the  absence  of  elevators  for 
elevated  railway  stations.  The  problem  is  one  for  inventors, 
rather  than  for  contractors. 

An  engineering  periodical  wonders  why  there  is  not  in  the 
market  a  ball-bearing  for  steam  engine  shafting.  The  bicycle 
ball-bearing  will  not  do  for  large  machinery. 

The  present  locking  nut,  with  steel  spiral,  for  railways  often 
fails.  In  fact,  rusting  the  nut  on  is  about  as  efficient. 

If  a  house  carries  on  business  between  New  York  and  Den- 
ver, ten  days  elapse  before  important  papers  can  be  returned.  I 
for  one  would  pay  $i  postage  on  many  legal  papers  if  they 
would  go  to  any  point  in  the  West  during  about  one  night. 
Rapid  transit  for  commercial  and  legal  papers  is  next  in  import- 
ance to  the  telephone. 

In  manufacturing  illuminating  gas  from  steam,  the  product 
being  called  water  gas,  the  steam  is  passed  through  white-hot 
coals.  It  is  noticed  that  a  large  portion  of  the  incandescent 
coal  at  the  point  where  the  steam  enters  is  cooled  down  to  such 
a  temperature  as  to  become  useless  for  decomposing  the  water 
into  oxygen  and  hydrogen. 

That  which  is  not  known  as  physically  impossible  is  worth 
consideration  by  the  inventor.  At  the  time  of  writing,  there  is  a 
great  drought  over  this  section  of  the  country,  and  yet  within  a 
mile  above  our  heads  have  hung  for  several  days  enough  clouds 
to  form  a  deluge.  It  is  difficult  to  support  things  in  the  thin  air, 
and  yet  those  clouds  float  there  as  if  the  air  were  mercury  or 
iron.  No  engineer  can  give  a  reason  why  some  water  at  least 
cannot  be  obtained  from  such  clouds.  It  is  the  inventor's  place 
to  consider  this  problem  with  the  help  of  all  the  knowledge  he 
can  possibly  get. 

Some  of  the  difficulties  in  storage  batteries  are  the  buckling 
of  the  plates,  whereby  they  bend  toward  each  other,  and  neutral- 
ize the  current  by  touching  each  other;  falling  off  of  the  active 
material;  formation  of  sulphate  of  lead,  which  increases  the  resist- 
ance, and  which  is  formed  at  the  loss  of  an  equivalent  amount 


150 

of  the  active  oxides  of  lead  ;  the  great  weight  of  a  battery;  the 
eating  away  of  the  terminals  where  they  pass  out  of  the  elec- 
trolyte ;  and  partial  polarization. 

In  the  form  of  air-brake  systems  using  the  direct  pressure  of 
the  air,  the  engineer  too  often  uses  too  much  pressure,  thereby 
wearing  the  wheels  oval  by  sliding.  What  is  the  prevention  or 
tell-tale  ? 

At  seashores,  pumps  driven  by  the  waves  are  becoming  com- 
mon, but  for  driving  machinery  a  difficulty  still  exists,  arising 
from  the  varying  amplitude  of  the  waves. 

The  storage  system  is  perfection,  as  far  as  the  public  are  con- 
cerned, but  death  to  the  operating  company,  on  account  of  over 
50  per  cent,  of  the  current  being  lost,  solely  by  the  process  of 
storing.  The  overhead  system  is  highly  economical,  but  the 
public  reject  it  for  streets  having  handsome  residences.  The 
surface  or  underground  system  embodies,  in  theory,  the  best 
elements  of  both  the  former  ;  but — can  leakage  and  danger  be 
prevented  ? 

Since  hotels  will  insist  in  carrying  out  the  law  (requiring  fire- 
escapes),  by  supplying  in  each  room  a  combustible  rope  which 
only  serves  to  burn  and  let  the  inexperienced  circus  actor  drop, 
why  cannot  architects  or  others  acquainted  with  building  pro- 
vide an  internal  fire-escape  of  a  fireproof  nature — or  provide 
that  which  is  a  part  of  the  building  and  not  an  attachment  ? 
This  seems  easy  enough,  but  the  problem  consists  in  getting  that 
construction  which  will  take  well  with  the  style  of  man  who  pays 
for  the  building. 

A  telegraphic  relay  depends  upon  a  spring  for  its  delicate  ad- 
justment, but  the  spring  soon  loses  it  elasticity.  Can  a  relay  be 
constructed  so  as  not  to  be  dependent  upon  the  elasticity  of  a 
spring  ? 

A  very  common  accident  on  cable  railways  is  that  where 
people  are  thrown  off  from  the  platform  when  the  engineer  puts 
the  final  grip  upon  the  cable.  A  peculiar  motion  occurs,  which 
has  thrown  some  of  the  nimblest  men. 

In  large  buildings  in  New  York,  and  other  large  cities,  it 
occupies  the  letter  carrier  about  ^  hour  to  distribute  the 
letters  in  each  building.  Is  it  possible  to  devise  advantageous 
mechanical  means  for  doing  this  ?  It  depends  upon  what  the 
system  is  when  invented. 

Considerable  trouble  is  experienced  by  steam  boiler-makers 
because  the  tubes  and  shell  separate,  due  to  large  contractions 
and  expansions  in  cooling  and  heating.  The  cylindrical  part  of 
the  Shell  has  a  different  degree  of  expansion  and  contraction 
from  that  of  the  tubes.  The  problem  is  to  provide  the  best 


151 

means  for  preventing  the  tubes  from  becoming  loose  in  the  ends 
of  the  boiler. 

To  prolong  the  durability  of  taps  for  cutting  internal  screws, 
the  difficulty  is  experienced,  because  the  greater  part  of  the 
tapping  is  done  by  the  forward  end  of  the  tap,  while  the  re- 
mainder remains  practically  unworn. 

In  the  present  fire  extinguisher,  operated  by  the  melting  of 
solder  by  the  heat  of  the  fire,  to  let  water  out  of  a  vessel  upon  the 
fire,  the  solder  becomes  solidified  by  the  cold  water,  thereby  pre- 
venting the  flow  of  water,  at  least  only  through  the  very  small 
hole  made  at  the  beginning  of  the  melting.  Consequently,  this 
easily  fusible  metal  stopper  seems  to  have  its  defects. 

No  subject  is  more  inviting  to  inventors  capable  of  design- 
ing complicated  mechanisms  than  that  of  setting  up  type  by  a 
device  like  a  typewriter.  The  latest  is  that  in  which  the  type 
metal  is  melted,  while  the  keys  are  for  feeding  the  fused  metal 
into  a  proper  matrix  for  each  letter.  After  use,  the  type  are  up- 
set and  melted  over  again.  This  is  certainly  a  novel  idea,  and 
it  is  being  used  by  one  or  two  large  newspaper  establishments, 
but  it  is  not  applicable  to  the  ordinary  printing-house.  The 
principal  cost  of  getting  printing  done  is  that  for  the  setting  up. 
Why  should  this  not  be  capable  of  cheapness  equal  to  that  of 
typewriting  where  a  copyist  can  operate  15,000  letters  in  an  hour  ? 

Chemists  experience  difficulty  in  keeping  hydrofluoric  acid, 
as  it  attacks  glass,  while  platinum — very  expensive — is  about 
the  only  metal  it  does  not  attack.  Earthenware  is  not  suitable. 
Bottles  have  been  made  of  wax,  but  the  weakness  is  a  defeat  to 
its  success.  Rubber  and  lead  are  attacked,  although  slowly, 
making  the  acid  impure,  and  experiencing  leakage  after  stand- 
ing any  considerable  length  of  time. 

In  electric  welding,  the  larger  part  of  the  current  passes,  and 
is  not  converted  into  heat,  as  desired,  at  the  point  of  welding — 
of  course,  the  more  heat  there  is  the  more  current  there  is  in  the 
circuit,  but  still  the  principles  of  science  do  not  teach  that  the 
proportion  of  heat  to  current  cannot  be  increased.  How  can  it 
be  brought  to  an  efficient  maximum  ? 

In  view  of  more  injury  arising  from  stoves  in  railway  acci- 
dents than  from  the  accidents  themselves,  is  it  possible  to  apply 
electricity  to  heating  the  cars?  It  depends  upon  the  results  ob- 
tained by  an  analytical  and  synthetical  consideration  of  this 
problem. 

It  is  reported  by  butchers  that  artificial  hatching  of  chickens 
is  becoming  a  failure.  The  chickens  are  hatched  all  right  and 
live  a  few  months,  but  are  very  thin  and  most  of  them  die. 
There  seems  an  important  difference  between  the  natural  and 


152 

artificial.  In  the  former  the  chickens  are  out  of  doors  in  the 
warm  weather  with  absolutely  pure  air — in  the  latter,  they  are 
in  a  close  place,  with  scarcely  anything  to  breathe  but  carbonic 
acid  gas,  or  other  impurities,  coming  from  the  heating  process. 
Does  not  the  delicate  health  of  the  chickens  arise  from  bad  air'? 
Remember  that  telephony  was  becoming  a  failure  before  the 
invention  of  the  carbon  transmitter,  which  produced  such  good 
results  as  to  make  a  grand  success. 

The  subject  of  electric  railways  connecting  cities  and  sup- 
plying even  greater  rapid  transit  than  by  steam  is  being  agitated. 
The  armature  would  be  mounted  upon  the  car  axle,  thus  elimi- 
nating entirely  all  the  numerous  mechanisms  of  the  locomotive. 
There  is  one  difficulty,  however.  The  present  trolley  is  well 
enough  for  slow  speeds;  but  something  radically  different  and 
superior  must  be  invented  for  making  continuous  electric  con- 
tact between  a  stationary  conductor  and  a  train  going  at,  say,  90 
miles  per  hour. 

There  is  no  apparent  reason  why  the  governing  of  a  steam 
engine  should  not  be  accomplished  efficiently  by  electric  means 
for  adjusting  the  throttle  valve.  This  problem  has  been  at- 
tacked, but  in  such  a  crude  manner  that  the  ordinary  mechanical 
governors  have  not  been  abandoned. 

Why  do  passengers  on  a  railway  train  become  worn  out,  when 
the  pleasant  ride  through  a  beautiful  country  should  be  bene- 
ficial ?  It  is  due  to  the  smoke  and  coal  gas  from  the  locomotive. 
To  prevent  production  of  these  nuisances  is  substantially  im- 
possible; but  how  about  a  design  of  a  car  or  a  device  whereby 
people  may  have  the  pure  air  to  breathe? 

Carbon  depositied  by  heat  is  well  known  as  superior  to  car- 
bonized wood.  The  difficulty  is  to  manufacture  it  in  the  form 
of  carbon  filaments  for  incandescent  electric  lamps. 

Murders  take  place  by  pistol  shots  in  hotels,  and  are  not 
known  until  the  escape  of  the  criminal.  Provide  protected  auto- 
matic means  for  giving  a  signal  at  the  hotel  office. 

In  the  manufacture  of  carbon  filaments,  the  same  break  in 
large  proportion,  from  shrinking  about  25  per  cent.  The  problem 
is  to  carbonize  with  less  breakage. 

Prof.  Nichols,  of  Cornell,  has  proposed  obtaining  incandes- 
cence for  electric  lamps  by  providing  means  whereby  the  in- 
candescing substance  is  magnesia  or  similar  infusible  and  incom- 
bustible substance,  of  a  white  color,  instead  of  carbon.  The  in- 
candescence is  reached  at  a  much  lower  temperature  in  the 
former,  and  therefore  also  follows  greater  economy. 

In  the  manufacture  of  arc  lamp  carbons,  the  present  diffi- 
culty is  in  baking  them  so  that  all  the  rods  are  at  a  uniform 


153 

temperature.  Some  are  found  baked  perfectly  and  others  only 
partially,  so  that  the  operation  must  be  repeated  for  a  large 
per  cent. 

One  of  Jhe  most  difficult  problems  known  is  to  be  able  to 
renew  carbon  filaments  without  throwing  away  the  bulbs. 

Who  is  to  be  the  first  to  provide  an  incandescent  'electric 
lamp  which  will  not  "  blacken  "  by  carbon  depositing  on  the 
inside  of  the  bulb,  or  who  will  produce  equivalent  means  for 
removing  this  objection  to  the  lamp  ? 

Wanted,  a  good  design  for  electric  lamp  bulbs,  having  a 
minimum  interior  space,  to  shorten  time  and  expense  for 
exhausting,  which  is  the  most'  expensive  step  in  its  manu- 
facture. 

Door  bell  hangers  do  not  recommend,  and  some  refuse  jobs, 
in  equipping  buildings  with  electric  bells,  because  repair  is  so 
often  needed.  The  difficulty  seems  to  lie  in  the  sparking;  evil 
results  from  sparking  both  at  the  bell  and  at  the  push  button. 
Otherwise  the  electric  bell  is  more  advantageous  than  the  me- 
chanical. 

Incandescent  lamps,  to  be  efficient,  are  limited  to  a  maximum 
of  50  candle  power,  and  arc  lamps,  to  a  minimum  of  1,000  c.  p. 
The  problem  is  to  furnish  a  lamp  equally  as  practical,  but  of  a 
candle  power  of  about  100  to  200. 

There  is  a  continual  call  among  housekeepers  for  means  of 
"  turning  down  "  the  incandescent  lamp.  Tell  them  that  they 
may  as  well  turn  it  out,  as  they  need  no  match  to  light  it  with, 
and  they  will  reply  that  it  is  not  a  question  of  economy,  but  of 
convenience  for  a  night  lamp,  or  as  a  means  of  showing  as  a 
signal  where  the  lamp  is  in  an  otherwise  dark  room.  The  rhec- 
stat  has  been  proposed,  and  one  or  two  other  schemes,  but  the 
commercially  successful  way  still  seems  to  be  wanting.  The  re- 
sult to  be  obtained  is  the  production  of  an  adjustable  intensity 
of  light,  at  the  limits  of  one  candle  power  and  the  maximum. 

At  high  speeds,  trains  jump  the  track,  and  serious  accidents 
occur.  This  generally  may  be  looked  upon  by  inventors  as  in- 
evitable; but  such  a  decision  should  never  be  conceded  by  an 
inventor  until  he  has  analyzed  the  causes  of  such  accidents,  and 
located  the  fault,  whether  with  the  wheels,  the  construction  of 
the  rails,  or  the  speed  relatively  to  the  weight;  consider  also 
whether  prevention  or  cure  should  be  aimed  at. 

After  the  production  of  reading  matter  by  the  typewriter  one 
must  count  the  words.  Where  the  matter  is  located  irregularly 
much  time  is  needed.  A  good  and  cheap  device  for  counting 
the  number  of  words  made  by  a  typewriting-machine  would 
certainly  have  a  market  among  typewriter  copyists. 


154 

Reference  is  made  among  these  problems  to  a  substitute  for 
the  carbon  telephone  transmitter,  in  order  to  give  another  in- 
ventor a  chance  to  benefit  himself  and  others,  after  the 
monopoly  has  been  so  long  held  by  another  party.  A  similar 
case  is  found  in  time  locks  for  safes.  A  time  lock  is  of  no 
value  if  it  can  be  opened  by  any  secret,  before  the  time  set. 
But  suppose  the  clockwork  stops  before  that  time.  There 
should  be  secret  means  for  opening  it  under  this  condition.  In 
the  present  system  the  time  lock  is  combined  in  such  a  manner 
with  a  combination  lock  that  if  the  clock  should  stop  before  the 
time  set  for  opening  the  safe,  the  manufacturers  can  give  the 
owners  a  combination  which  will  open  it ;  but  this  combination 
will  not  open  it  if  the  clock  does  not  stop.  It  seems  a  possibility 
that  inventors  could  provide  means  whereby  the  owners  could 
open  it  under  the  sole  condition  that  the  clockwork  stops  be- 
fore the  proper  time.  It  must  be  remembered  that  there  must 
be  no  means  whatever  whereby  the  safe  can  be  opened  before 
the  time  set,  while  the  clock  is  still  working,  or  else  the  object 
of  the  time  lock  is  a  failure,  being  to  prevent  a  thief  from 
torturing  the  men  with  the  secret  to  open  the  safe. 

A  problem  needing  much  attention  by  inventors  having 
considerable  mechanical  knowledge  is  the  turn-out  for  trolleys, 
operative  when  the  electric  car  passes  upon  a  side  track. 
Although  the  present  form  only  fails  a  few  times  a  week,  it  is 
quite  a  wonder  it  does  not  always  fail. 

The  trolley  support  for  holding  the  trolley  upward,  against 
the  line,  is  at  present  made  in  such  a  variety  of  forms  that 
this  alone  is  evidence  that  there  is  probably  no  best  trolley 
arm. 

It  is  scarcely  possible  to  obtain  a  glass  of  sweet  milk  in 
restaurants  if  a  thunder-storm  is  occurring  within  a  hundred 
miles  or  so.  The  cause  of  acidity  is  well  known,  but  the  prob- 
lem of  preventing  it  seems  to  be  little  considered.  Lightning, 
/.  e.,  the  electricity,  changes  oxygen  into  the  allotropic  state  of 
ozone,  which  has  a  strong  affinity  for  certain  elements  of  the 
milk,  causing  an  acid  to  form.  This  is  a  problem  for  chemists, 
although  its  solution  in  a  simple,  mechanical  manner  may 
perhaps  be  that  which  is  conveniently  applicable  in  the 
kitchen  and  restaurants  by  servants. 

A  periodical  states  that  one  of  the  difficulties  attending  the 
use  of  the  telephone,  on  long  lines,  is  in  suppressing  "  overhear- 
ing "  from  other  wires,  due  to  induction  or  leakage.  In  using 
the  instrument,  it  is  often  annoying  to  have  your  conversation 
heard  by  those  other  than  the  one  you  are  supposed  to  be 
addressing.  A  present  method  is  to  have  a  return  wire  instead 


155 

of  using  the  earth,  but  the  expense  of  a  line  is  thereby  nearly 
doubled. 

To  provide  such  means  that  the  vibrations  of  air  produced 
by  wagons, drains,  horse-cars,  &c.,  can  be  changed  in  number 
per  second  to  considerably  below  that  rate  which  does  not  pro- 
duce sound  to  the  ear,  or  to  increase  to  such  a  rate  as  to 
eliminate  the  sensation  of  sound,  or  in  other  directions  of 
development,  let  the  inventor  try  to  turn  sound  into  silence,  as 
far  as  the  ear  is  concerned.  The  scientist  can  go  so  far  as  to 
tell  the  inventor  that  there  is  known  no  reason  why  it  cannot  be 
done. 

One  of  the  difficulties  in  electric  railway  departments  is  that 
of  repairing  overhead  lines,  which  are  high  in  the  air. 

The  same  cause,  "  retardation,"  which  prevents  rapidity  of 
telegraphic  transmission  at  long  distances,  is  an  important 
cause  in  preventing  telephonic  transmission  at  long  distances. 

It  is  now  apparently  conceded  that  the  last  car  on  a  train  is 
the  most  dangerous.  A  friend  facetiously  remarked  that  the 
railway  company  ought  not  to  have  a  last  car. 

Heat,  light,  and  sound  may  be  radiated,  reflected  and  in 
some  instances  transmitted  through  substances,  and  concen- 
trated into  a  focus.  Can  these  properties  be  said  to  be  true  of 
electricity,  and  if  so,  what  are  their  applications  ? 

During  the  past  two  or  three  years  the  alternating  electric 
current  has  become  widely  applied  in  connection  with  electric 
lighting.  There  is  to-day  no  motor  which  can  be  operated 
commercially  on  a  large  scale  by  such  a  current.  Conse- 
quently, a  system  of  electric  power  cannot  be  combined  with  a 
system  of  alternating  current  lighting.  Motors  for  alternating 
currents  have  been  invented;  but  on  account  of  their  extremely 
low  efficiency,  are  applicable  only  to  small  power,  as  for  driving 
small  ventilating  fans.  It  has  been  reported  that  a  large 
capitalist  and  manufacturer  offered  the  sum  of  one  million  dol- 
lars for  a  patent  on  a  successful  alternating  current  motor  for 
railways,  and  that  electricians  have  agreed  that  a  monument  will 
be  erected  in  honor  of  the  inventor  before  he  dies,  and  that  in 
other  ways  he  will  be  rewarded  for  solving  one  of  the  greatest 
difficulties  in  connection  with  electric  power.  The  names  of  the 
present  inventors  of  commercially  successful  alternating  current 
motors,  for  very  small  power,  should  be  mentioned  in  this  con- 
nection. They  are  :  Prof.  Elihu  Thomson,  Nikola  Tesla, 
Ludwig  Gutmann,  Lieut.  F.  Jarvis  Patten,  Chas.  J.  Van  Depoele, 
and  Prof.  W.  A.  Anthony,  with  his  two  colleagues,  Messrs. 
Jackson  and  Ryan.  In  the  space  of  about  only  two  or  three 
years  these  inventors  discovered  valuable  principles  which  are 


150 

perhaps  merely  the  beginning  of  further  developments,  either  by 
themselves  or  others. 

The  best  alternating  motor  at  present  is  the  synchronizing 
motor,  combined  with  the  improved  small  motor  for  starting. 

Since  the  improvement  of  Faure,  the  electro-chemical 
storage  battery  has  been  introduced  on  a  commerical  scale  ;  but 
if  it  were  as  economical  for  railways  as  the  overhead  system, 
the  latter  would  become  extinct.  The  storage  system  at  present 
finds  its  way  only  where  economy  is  not  to  be  considered.  The 
problem  is  one  of  the  most  difficult  of  the  day,  since  the  trans- 
mission of  electrical  energy,  in  storing  and  in  recovering,  in- 
volves a  loss  each  time.  Thus  to  convert  electrical  into 
chemical  energy,  and  then  chemical  into  electrical,  necessi- 
tates a  total  loss,  even  in  the  laboratory,  of  about  twenty-five 
per  cent,  and  in  practice  more  yet  on  account  of  mechanical 
difficulties.  One  more  improvement  equal  in  magnitude  to 
that  of  Faure  over  Plante  would  make  the  storage  system  a 
grand  success. 

The  wonderful  invention  of  photography  has  not  yet  been 
superseded  by  that  of  photographing  colors.  The  man  with  red 
hair  has  dark  hair  in  his  photograph,  and  for  that  he  may  be  thank- 
ful; but  the  rosy-cheeked  girl,  with  beautifully  tinted  ribbons, 
and  adorned  with  variegated  flowers,  would  greatly  enlarge  the 
sale  of  cameras  if  her  picture  would  result  in  a  reproduction  of 
her  colors.  This  subject  was  attacked  in  the  early  days  of  the 
art;  but  it  may  remain  for  electricians,  especially  electro- 
chemists,  to  combine  an  appropriate  electrical  principle  with  a 
chemical  principle  to  solve  the  problem.  Some  substances 
assume  different  colors  under  the  influence  of  light,  and  it  is 
also  true  under  the  influence  of  electrolytic  action. 

Perpetual  motion  is  impossible,  but  the  forces  of  nature,  as 
the  wind,  falling  water,  the  heat  and  light  of  the  sun,  the  rise  and 
fall  of  tides,  the  ocean's  billows,  the  earth's  magnetism,  evapor- 
ation, and  lighting  are  intermittent,  and  therefore,  although  un- 
trustworthy in  their  natural  condition,  are  nevertheless  forms  of 
energy  which  cost  nothing,  and  which  are  at  the  disposal  of  the 
future  inventors  for  storage,  and  for  sale  in  the  shape  of  heat, 
light  power,  electricity,  and  chemical  action.  To  prove  that 
there  is  immense  power  in  the  chemical  rays  of  the  sun,  it  is 
only  necessary  to  fill  a  vessel  with  a  mixture  of  hydrogen  and 
chlorine  gas,  close  it  hermetically  and  expose  it  to  the  sun.  The 
vessel  is  blown  to  atoms,  although  the  mixture  is  unaffected  in 
the  dark  or  when  exposed  to  merely  the  heat  of  the  sun.  The 
actinic  or  chemical  rays  are  a  powerful  agency  on  a  cloudy  day, 
sufficient  actinic  rays  being  present  to  cause  the  combination  to 


157 

take  place  gradually  with  the  formation  of  a  minute  drop  of  hy- 
drochloric acid. 

Yes,  there  is  enough  power  there.  The  power  is  cheap.  If 
the  day  is  cloudy,  the  time  for  storing  need  simply  be 
lengthened.  Even  if  every  house  has  no  yard  where  the  device 
can  be  exposed  to  light,  yet  there  is  a  roof  to  every  dwelling 
exposed  to  the  full  daylight,  and  its  size  is  proportional  to 
the  size  of  the  house  and  therefore  to  the  number  of  lamps 
therein. 

At  present,  the  commercial  form  of  electricity  is  obtained 
from  fuel,  such  as  coal ;  but  the  heat  is  first  changed  into  me- 
chanical motion,  which  is  then  changed  into  electrical  energy. 
Electricity  may  be  changed  directly  into  heat  or  light.  The 
problem  is  to  change  the  force  of  heat  directly  into  electrical 
energy.  A  steam  locomotive  is  more  ecconomical  by  far  than 
an  electric  railway  system  ;  but  a  heat  electric  engine  would 
certainly  be  economical. 

From  the  beginning  of  the  electric  age  until  the  present 
striking  improvements  have  been  made  in  electric  generation, 
and  there  is  no  reason  for  expecting  them  to  stop. 

One  of  the  greatest  difficulties  with  the  present  dynamo  is 
apparent  when  it  is  realized  that  the  only  part  needing  atten- 
tion is  the  commutator,  which  must  be  kept  from  sparking. 
Each  dynamo  could  be  left  to  take  care  of  itself  if  it  were  not 
for  this  difficulty.  In  electric  railways,  the  commutator  is  in- 
jured by  dust,  the  sparking  wears  it  out  rapidly,  and  the  machine 
on  this  account  alone  needs  attention.  There  is  needed  an  elec- 
tric motor  that  can  be  locked  up  in  a  box  and  left  there  for 
weeks  without  attention,  the  current  being  conveyed  to  it  by 
wires  passing  through  the  box.  This  is  only  one  of  the  fields 
needing  a  commercial  means  of  preventing  sparking  upon  the 
rupture  of  reversal  of  a  current. 

At  last  the  electric  meter  appears  to  have  met  with  commer- 
cial success,  one  form  being  electro-chemical  and  the  other 
electro-mechanical.  But  I  would  not  be  surprised  if  another 
meter  were  invented  far  outweighing  all  others  in  simplicity  of 
construction,  accuracy  of  measurement,  durability  and  con- 
venience. 

One  of  the  greatest  difficulties  in  the  manufacture  of  dy- 
namos and  electric  motors  is  the  apparent  necessity  of  boring 
the  pole-pieces  in  order  that  the  same  may  be  at  the  mininum 
inductive  distance  to  the  armature. 

A.  Reckenzaun,  C.  E.,  states  in  a  paper  before  the  American 
Institute  of  Electrical  Engineers:  "The  problem  of  devising 
suitable  gearing  for  street  cars  carrying  their  own  motors  has 


158 

been  and  is  still  of  the  greatest  importance.     The  conditions  to 
be  satisfied  are  by  no  means  simple." 

Nikola  Tesla  points  out  that  the  next  necessary  step  in  the  fur- 
ther development  of  light  by  great  frequency  of  alternations  of 
current,  combined  with  very  high  potential,  is  the  production  of  an 
insulator  which  will  not  be  injured  by  the  charge  and  discharge. 
He  finds  great  difficulty  because  no  induction  coil  so  far  made  is 
able  to  withstand  the  currents  of  high  frequency  and  potential 
which  are  obtainable. 

The  last  lines  of  the  following  clipping  will  indicate  that  the 
inventor's  power  is  needed  in  a  certain  detail  of  marine 
machinery: 

"Another  Ship  Disabled. 

"  NEW  YORK,  July  14. — The  tramp  ship  Endymion  is  re- 
ported to  have  been  met  on  July  loth  with  her  crank  broken, 
struggling  to  reach  New  York.  She  declined  the  assistance  of 
passing  ships  and  is  expected  off  Fire  Island  to-day.  Tugs  are 
in  readiness  to  meet  her  when  sighted.  The  Endymion  is  from 
Banon,  England.  She  is  the  fourth  ship  which  has  suffered  in 
this  manner  in  a  month." 

In  1881,  Prof.  Thurston  presented  the  following  problem  be- 
fore the  Society  of  Mechanical  Engineers.  He  says: 

"  The  second  of  these  greatest  of  inventors  is  he  who  will 
teach  us  the  source  of  the  beautiful,  soft-beaming  light  of  the 
fire-fly  and  the  glow-worm,  and  will  show  us  how  to  produce 
this  singular  illuminant,  and  to  apply  it  with  success  practically 
and  commercially.  This  wonderful  light,  free  from  heat  and 
from  consequent  loss  of  energy,  is  nature's  substitute  for  the 
crude  and  extravagantly  wasteful  lights  of  which  we  have, 
through  so  many  years,  been  foolishly  boasting.  The  dynamo- 
electrical  engineer  has  nearly  solved  this  problem.  Let  us  hope 
that  it  may  be  soon  fully  solved,  and  by  one  of  those  among  our 
own  colleagues  who  are  now  so  earnestly  working  in  this  field, 
and  that  we  may  all  live  to  see  him  steal  the  glow-worm's  light, 
and  to  see  the  approaching  days  of  Vril  predicted  so  long  ago  by 
Lord  Lytton." 

In  telegraphy,  condensers  have  been  used  with  advantage  in 
preventing  the  bad  effects  of  self-induction,  sparking,  extra 
currents,  &c.  It  has  many  times  been  pointed  out  that  if  a 
durable  condenser  for  large  currents,  such  as  are  used  in  elec- 
tric light  and  power  stations,  could  be  invented,  the  efficiency  of 
electric  motors  (especially  the  alternating)  and  dynamos  could 
be  greatly  increased.  The  objection  to  all  known  condensers 
for  large  currents  is  that  the  insulation  is  easily  punctured. 


159 

burned  or  otherwise  injured  by  the  charges  they  receive,  render- 
ing the  condenser  useless. 

At  the  time  of  writing,  the  decision  of  Judge  Wallace  has 
upheld  the  Edison  filament  patent.  How  easy  it  would  be, 
therefore,  to  sell  to  an  opposing  party  an  invention  by  which 
the  current  can,  without  a  filament,  be  subdivided  for  producing 
lights  of  from  10  to  20  candle  power  each  in  as  economical  and 
desirable  a  manner  as  by  the  use  of  the  present  incandescent 
electric  lamp. 

Since  the  introduction  of  the  incandescent  electric  lamp 
attempts  have  been  made  whose  object  is  to  use  the  great  heat 
of  a  gas  flame  for  producing  greater  intensity  of  light.  In  the 
ordinary  flame  only  about  8  per  cent,  is  light  energy,  the  re- 
maining 92  per  cent,  being  heat. 

Some  effective  way  of  preventing  "  sweat  spots  "  and  "  chill 
cracks  "  in  cast  car  wheels  is  called  for. 

Recently,  a  telephone  manager  received  such  severe  shocks 
as  to  be  thrown  down  insensible,  and  the  telephone  wire  was 
setting  fire  to  the  building.  Others  tried  to  get  at  the  wire  to  cut 
it,  but  were  treated  likewise.  They  telephoned  to  six  different 
electric  light  stations  to  turn  off  the  lights  before  the  remedy 
was  effected.  What  is  the  best  way  to  prevent  such  mishaps  in 
the  future,  or  how  can  any  existing  devices  be  made  com- 
mercially valuable  ? 

In  feed  cutters  and  similar  machines  great  injury  is  often 
produced  by  unusual  and  sudden  resistance  coming  upon  the 
machine.  How  can  the  small  pulley  be  so  attached  as  to  be- 
come loosened  at  a  predetermined  strain  thereon  and  be  subse- 
quently adjustable  ? 

How  long  shall  explosions,  fires,  deaths,  &c.,  continue  from 
the  use  of  oil  lamps  ?  Until  a  lamp  is  made  which  can  be  upset 
or  tumbled  around  on  the  floor  with  no  other  injury  than  the 
breaking  of  the  chimney,  the  inventor  should  feel  somewhat 
responsible  for  damages. 

In  hunting,  the  tremendous  noise  and  re-echoing  of  the  gun 
frightens  the  game,  so  that  it  is  usually  necessary  to  walk  about 
a  mile  to  meet  more  game.  In  other  ways  the  noise  is  objection- 
able. Cannot  the  inventor  devise  means  whereby  silent  and 
effective  hunting  may  be  carried  on.  It  would  be  a  great  boon 
to  the  sportsman. 

Since  the  inception  of  photography  it  has  doubtlessly 
occurred  to  many  that  it  is  probable  that  some  inventor  may 
be  able  to  photograph,  and  especially  to  print  photographs  from 
negatives  in  the  dark,  by  the  use  of  substances  sensitive  to  heat 
rays.  The  secret  for  the  inventor  to  discover  is  that  chemical 


160 

or  combination  of  chemicals  which  will  be  sensitive  to  heat 
rays.  A  difficulty  he  will  meet,  not  found  in  the  case  of  light, 
is  that  heat  is  conducted.  This  difficulty,  however,  may  not  be 
insurmountable.  Photographers  have  plenty  of  time  to  spare 
and  plenty  of  printing  to  do  on  rainy  days  and  in  the  evenings. 

George  Gibbs,  M.  E.,  in  a  paper  before  the  Western  R.  R. 
Club,  proposed  a  problem  as  follows,  relating  to  car  lighting  : 

"  A  favorite  scheme  for  obtaining  electricity  at  a  low  cost 
seems  to  have  been  to  connect  the  dynamo  to  a  car  axle;  but 
the  difficulties  of  obtaining  regular  motion  and  current,  and 
providing  light  when  the  train  stops,  have  necessitated  the  em- 
ployment of  accumulators  as  regulators  and  auxiliaries.  In  these 
plans  automatic  appliances  are  provided  to  cut  off  the  current 
from  the  dynamo  when  the  speed  of  the  train  falls  below  a 
certain  rate,  and  to  deliver  the  current  to  the  batteries  in  the 
same  direction,  no  matter  which  way  the  train  may  move.  Many 
foreign  railways  have  tried  this  plan,  the  most  successful  in- 
stance being  of  the  "Pullman  Limited"  on  the  London, 
Brighton  &  South  Coast  Railway,  where  the  system  is  still  in 
use.  The  main  difficulty,  and  one  which  the  International  Rail- 
way Congress  states  has  not  been  solved  satisfactorily,  is  the 
method  of  transmission  of  power  from  the  axle  to  the  dynamo." 


CHAPTER  XXIV. 
CONCLUSION. 


I  HAVE  spoken  of  pecuniary  reward.  Men  have  made  for- 
tunes, both  as  inventors  and  as  capitalists  investing  in  inven- 
tions. Whether  wealth  is  obtained  or  not,  one  thing  will  result 
from  the  introduction  of  a  useful  invention,  as  surely  as  heat 
results  from  combustion,  and  that  is,  a  name  which  will  last 
forever,  as  an  honor  both  to  the  inventor  and  to  his  descendants. 

Napoleon's  name  also  probably  will  last  forever,  but  whereas 
he  conquered  nations,  by  producing  certain  blessings  at  great 
sacrifice  of  human  life,  benefit  without  sacrifice  has  been  pro- 
duced by  Archimede's  screw,  Barker's  mill,  Watt's  steam  engine, 
Stephenson's  locomotive,  Galvani's  electric  battery,  Faraday's 
electric  motor,  Davy's  safety  lamp,  Bunsen's  burner,  Morse's 
telegraph,  Gramme's  dynamo,  Prof.  Thomson's  electric  welding 
process,  Plante"  and  Faure's  storage  of  electricity,  Edison's 
incandescent  electric  lamp,  phonogragh  and  carbon  transmitter, 


lei 

Bell's  telephone,  Westinghouse's  air  brake,  and  Pullman's 
vestibule  cars. 

The  good  which  inventors  do  lives  after  them  ('tis  not  "  in- 
terred with  their  bones,")  and  their  inventions  are  better 
memorials  than  monuments  of  gold. 

People,  at  large,  live  and  think  in  the  Present ;  scholars  or 
the  learned  are  busy  with  the  Past ;  astronomers  predict  Future 
positions  of  the  heavenly  bodies ;  but  inventors  apply  the 
knowledge  of  the  Past,  look  into  the  Future  for  new  worlds  to 
conquer,  and  supply  the  Present  with  the  fruits  of  their  labors. 


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